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fix(curriculum): Convert blockquote elements to triple backtick syntax for JavaScript Algorithms and Data Structures (#35992)
* fix: convert js algorithms and data structures * fix: revert some blocks back to blockquote * fix: reverted comparison code block to blockquotes * fix: change js to json Co-Authored-By: Oliver Eyton-Williams <ojeytonwilliams@gmail.com> * fix: convert various section to triple backticks * fix: Make the formatting consistent for comparisons
This commit is contained in:
Randell Dawson
@@ -11,7 +11,13 @@ We can access the data inside arrays using <code>indexes</code>.
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Array indexes are written in the same bracket notation that strings use, except that instead of specifying a character, they are specifying an entry in the array. Like strings, arrays use <dfn>zero-based</dfn> indexing, so the first element in an array is element <code>0</code>.
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<br />
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<strong>Example</strong>
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<blockquote>var array = [50,60,70];<br>array[0]; // equals 50<br>var data = array[1]; // equals 60</blockquote>
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```js
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var array = [50,60,70];
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array[0]; // equals 50
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var data = array[1]; // equals 60
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```
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<strong>Note</strong><br>There shouldn't be any spaces between the array name and the square brackets, like <code>array [0]</code>. Although JavaScript is able to process this correctly, this may confuse other programmers reading your code.
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</section>
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@@ -9,7 +9,19 @@ videoUrl: 'https://scrimba.com/c/ckND4Cq'
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<section id='description'>
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One way to think of a <dfn>multi-dimensional</dfn> array, is as an <em>array of arrays</em>. When you use brackets to access your array, the first set of brackets refers to the entries in the outer-most (the first level) array, and each additional pair of brackets refers to the next level of entries inside.
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<strong>Example</strong>
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<blockquote>var arr = [<br> [1,2,3],<br> [4,5,6],<br> [7,8,9],<br> [[10,11,12], 13, 14]<br>];<br>arr[3]; // equals [[10,11,12], 13, 14]<br>arr[3][0]; // equals [10,11,12]<br>arr[3][0][1]; // equals 11</blockquote>
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```js
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var arr = [
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[1,2,3],
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[4,5,6],
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[7,8,9],
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[[10,11,12], 13, 14]
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];
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arr[3]; // equals [[10,11,12], 13, 14]
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arr[3][0]; // equals [10,11,12]
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arr[3][0][1]; // equals 11
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```
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<strong>Note</strong><br>There shouldn't be any spaces between the array name and the square brackets, like <code>array [0][0]</code> and even this <code>array [0] [0]</code> is not allowed. Although JavaScript is able to process this correctly, this may confuse other programmers reading your code.
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</section>
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@@ -9,7 +9,30 @@ videoUrl: 'https://scrimba.com/c/cLeGDtZ'
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<section id='description'>
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As we have seen in earlier examples, objects can contain both nested objects and nested arrays. Similar to accessing nested objects, Array bracket notation can be chained to access nested arrays.
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Here is an example of how to access a nested array:
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<blockquote>var ourPets = [<br> {<br> animalType: "cat",<br> names: [<br> "Meowzer",<br> "Fluffy",<br> "Kit-Cat"<br> ]<br> },<br> {<br> animalType: "dog",<br> names: [<br> "Spot",<br> "Bowser",<br> "Frankie"<br> ]<br> }<br>];<br>ourPets[0].names[1]; // "Fluffy"<br>ourPets[1].names[0]; // "Spot"</blockquote>
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```js
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var ourPets = [
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{
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animalType: "cat",
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names: [
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"Meowzer",
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"Fluffy",
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"Kit-Cat"
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]
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},
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{
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animalType: "dog",
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names: [
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"Spot",
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"Bowser",
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"Frankie"
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]
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}
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];
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ourPets[0].names[1]; // "Fluffy"
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ourPets[1].names[0]; // "Spot"
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```
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</section>
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## Instructions
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@@ -9,7 +9,24 @@ videoUrl: 'https://scrimba.com/c/cRnRnfa'
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<section id='description'>
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The sub-properties of objects can be accessed by chaining together the dot or bracket notation.
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Here is a nested object:
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<blockquote>var ourStorage = {<br> "desk": {<br> "drawer": "stapler"<br> },<br> "cabinet": {<br> "top drawer": { <br> "folder1": "a file",<br> "folder2": "secrets"<br> },<br> "bottom drawer": "soda"<br> }<br>};<br>ourStorage.cabinet["top drawer"].folder2; // "secrets"<br>ourStorage.desk.drawer; // "stapler"</blockquote>
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```js
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var ourStorage = {
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"desk": {
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"drawer": "stapler"
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},
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"cabinet": {
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"top drawer": {
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"folder1": "a file",
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"folder2": "secrets"
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},
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"bottom drawer": "soda"
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}
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};
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ourStorage.cabinet["top drawer"].folder2; // "secrets"
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ourStorage.desk.drawer; // "stapler"
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```
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</section>
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## Instructions
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@@ -10,7 +10,18 @@ videoUrl: 'https://scrimba.com/c/cBvmEHP'
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The second way to access the properties of an object is bracket notation (<code>[]</code>). If the property of the object you are trying to access has a space in its name, you will need to use bracket notation.
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However, you can still use bracket notation on object properties without spaces.
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Here is a sample of using bracket notation to read an object's property:
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<blockquote>var myObj = {<br> "Space Name": "Kirk",<br> "More Space": "Spock",<br> "NoSpace": "USS Enterprise"<br>};<br>myObj["Space Name"]; // Kirk<br>myObj['More Space']; // Spock<br>myObj["NoSpace"]; // USS Enterprise</blockquote>
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```js
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var myObj = {
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"Space Name": "Kirk",
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"More Space": "Spock",
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"NoSpace": "USS Enterprise"
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};
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myObj["Space Name"]; // Kirk
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myObj['More Space']; // Spock
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myObj["NoSpace"]; // USS Enterprise
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```
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Note that property names with spaces in them must be in quotes (single or double).
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</section>
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@@ -10,7 +10,16 @@ videoUrl: 'https://scrimba.com/c/cGryJs8'
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There are two ways to access the properties of an object: dot notation (<code>.</code>) and bracket notation (<code>[]</code>), similar to an array.
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Dot notation is what you use when you know the name of the property you're trying to access ahead of time.
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Here is a sample of using dot notation (<code>.</code>) to read an object's property:
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<blockquote>var myObj = {<br> prop1: "val1",<br> prop2: "val2"<br>};<br>var prop1val = myObj.prop1; // val1<br>var prop2val = myObj.prop2; // val2</blockquote>
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```js
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var myObj = {
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prop1: "val1",
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prop2: "val2"
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};
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var prop1val = myObj.prop1; // val1
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var prop2val = myObj.prop2; // val2
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```
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</section>
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## Instructions
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@@ -9,11 +9,30 @@ videoUrl: 'https://scrimba.com/c/cnQyKur'
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<section id='description'>
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Another use of bracket notation on objects is to access a property which is stored as the value of a variable. This can be very useful for iterating through an object's properties or when accessing a lookup table.
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Here is an example of using a variable to access a property:
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<blockquote>var dogs = {<br> Fido: "Mutt",
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Hunter: "Doberman",
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Snoopie: "Beagle"<br>};<br>var myDog = "Hunter";<br>var myBreed = dogs[myDog];<br>console.log(myBreed); // "Doberman"</blockquote>
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```js
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var dogs = {
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Fido: "Mutt", Hunter: "Doberman", Snoopie: "Beagle"
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};
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var myDog = "Hunter";
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var myBreed = dogs[myDog];
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console.log(myBreed); // "Doberman"
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```
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Another way you can use this concept is when the property's name is collected dynamically during the program execution, as follows:
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<blockquote>var someObj = {<br> propName: "John"<br>};<br>function propPrefix(str) {<br> var s = "prop";<br> return s + str;<br>}<br>var someProp = propPrefix("Name"); // someProp now holds the value 'propName'<br>console.log(someObj[someProp]); // "John"</blockquote>
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```js
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var someObj = {
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propName: "John"
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};
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function propPrefix(str) {
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var s = "prop";
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return s + str;
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}
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var someProp = propPrefix("Name"); // someProp now holds the value 'propName'
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console.log(someObj[someProp]); // "John"
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```
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Note that we do <em>not</em> use quotes around the variable name when using it to access the property because we are using the <em>value</em> of the variable, not the <em>name</em>.
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</section>
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@@ -11,7 +11,11 @@ videoUrl: 'https://scrimba.com/c/cM2KBAG'
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Now let's try to add two numbers using JavaScript.
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JavaScript uses the <code>+</code> symbol as an addition operator when placed between two numbers.
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<strong>Example:</strong>
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<blockquote>myVar = 5 + 10; // assigned 15</blockquote>
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```js
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myVar = 5 + 10; // assigned 15
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```
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</section>
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## Instructions
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@@ -9,7 +9,22 @@ videoUrl: 'https://scrimba.com/c/c3JvVfg'
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<section id='description'>
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In a <code>switch</code> statement you may not be able to specify all possible values as <code>case</code> statements. Instead, you can add the <code>default</code> statement which will be executed if no matching <code>case</code> statements are found. Think of it like the final <code>else</code> statement in an <code>if/else</code> chain.
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A <code>default</code> statement should be the last case.
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<blockquote>switch (num) {<br> case value1:<br> statement1;<br> break;<br> case value2:<br> statement2;<br> break;<br>...<br> default:<br> defaultStatement;<br> break;<br>}</blockquote>
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```js
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switch (num) {
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case value1:
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statement1;
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break;
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case value2:
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statement2;
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break;
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...
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default:
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defaultStatement;
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break;
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}
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```
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</section>
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## Instructions
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@@ -11,9 +11,26 @@ You may have heard the term <code>object</code> before.
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Objects are similar to <code>arrays</code>, except that instead of using indexes to access and modify their data, you access the data in objects through what are called <code>properties</code>.
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Objects are useful for storing data in a structured way, and can represent real world objects, like a cat.
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Here's a sample cat object:
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<blockquote>var cat = {<br> "name": "Whiskers",<br> "legs": 4,<br> "tails": 1,<br> "enemies": ["Water", "Dogs"]<br>};</blockquote>
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```js
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var cat = {
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"name": "Whiskers",
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"legs": 4,
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"tails": 1,
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"enemies": ["Water", "Dogs"]
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};
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```
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In this example, all the properties are stored as strings, such as - <code>"name"</code>, <code>"legs"</code>, and <code>"tails"</code>. However, you can also use numbers as properties. You can even omit the quotes for single-word string properties, as follows:
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<blockquote>var anotherObject = {<br> make: "Ford",<br> 5: "five",<br> "model": "focus"<br>};</blockquote>
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```js
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var anotherObject = {
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make: "Ford",
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5: "five",
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"model": "focus"
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};
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```
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However, if your object has any non-string properties, JavaScript will automatically typecast them as strings.
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</section>
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@@ -8,7 +8,20 @@ videoUrl: 'https://scrimba.com/c/caeJgsw'
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## Description
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<section id='description'>
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<code>if/else</code> statements can be chained together for complex logic. Here is <dfn>pseudocode</dfn> of multiple chained <code>if</code> / <code>else if</code> statements:
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<blockquote>if (<em>condition1</em>) {<br> <em>statement1</em><br>} else if (<em>condition2</em>) {<br> <em>statement2</em><br>} else if (<em>condition3</em>) {<br> <em>statement3</em><br>. . .<br>} else {<br> <em>statementN</em><br>}</blockquote>
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```js
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if (condition1) {
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statement1
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} else if (condition2) {
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statement2
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} else if (condition3) {
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statement3
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. . .
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} else {
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statementN
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}
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```
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</section>
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## Instructions
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@@ -10,9 +10,18 @@ videoUrl: 'https://scrimba.com/c/c7ynnTp'
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Comments are lines of code that JavaScript will intentionally ignore. Comments are a great way to leave notes to yourself and to other people who will later need to figure out what that code does.
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There are two ways to write comments in JavaScript:
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Using <code>//</code> will tell JavaScript to ignore the remainder of the text on the current line:
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<blockquote>// This is an in-line comment.</blockquote>
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```js
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// This is an in-line comment.
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```
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You can make a multi-line comment beginning with <code>/*</code> and ending with <code>*/</code>:
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<blockquote>/* This is a<br>multi-line comment */</blockquote>
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```js
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/* This is a
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multi-line comment */
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```
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<strong>Best Practice</strong><br>As you write code, you should regularly add comments to clarify the function of parts of your code. Good commenting can help communicate the intent of your code—both for others <em>and</em> for your future self.
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</section>
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@@ -9,10 +9,26 @@ videoUrl: 'https://scrimba.com/c/cKyVMAL'
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<section id='description'>
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There are many <dfn>Comparison Operators</dfn> in JavaScript. All of these operators return a boolean <code>true</code> or <code>false</code> value.
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The most basic operator is the equality operator <code>==</code>. The equality operator compares two values and returns <code>true</code> if they're equivalent or <code>false</code> if they are not. Note that equality is different from assignment (<code>=</code>), which assigns the value at the right of the operator to a variable in the left.
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<blockquote>function equalityTest(myVal) {<br> if (myVal == 10) {<br> return "Equal";<br> }<br> return "Not Equal";<br>}</blockquote>
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```js
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function equalityTest(myVal) {
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if (myVal == 10) {
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return "Equal";
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}
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return "Not Equal";
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}
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```
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If <code>myVal</code> is equal to <code>10</code>, the equality operator returns <code>true</code>, so the code in the curly braces will execute, and the function will return <code>"Equal"</code>. Otherwise, the function will return <code>"Not Equal"</code>.
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In order for JavaScript to compare two different <code>data types</code> (for example, <code>numbers</code> and <code>strings</code>), it must convert one type to another. This is known as "Type Coercion". Once it does, however, it can compare terms as follows:
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<blockquote>1 == 1 // true<br>1 == 2 // false<br>1 == '1' // true<br>"3" == 3 // true</blockquote>
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```js
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1 == 1 // true
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1 == 2 // false
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1 == '1' // true
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"3" == 3 // true
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```
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</section>
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## Instructions
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@@ -10,7 +10,14 @@ videoUrl: 'https://scrimba.com/c/cp6GbH4'
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The greater than operator (<code>></code>) compares the values of two numbers. If the number to the left is greater than the number to the right, it returns <code>true</code>. Otherwise, it returns <code>false</code>.
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Like the equality operator, greater than operator will convert data types of values while comparing.
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<strong>Examples</strong>
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<blockquote> 5 > 3 // true<br> 7 > '3' // true<br> 2 > 3 // false<br>'1' > 9 // false</blockquote>
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```js
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5 > 3 // true
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7 > '3' // true
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2 > 3 // false
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'1' > 9 // false
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```
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</section>
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|
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## Instructions
|
||||
|
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@@ -10,7 +10,14 @@ videoUrl: 'https://scrimba.com/c/c6KBqtV'
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The <code>greater than or equal to</code> operator (<code>>=</code>) compares the values of two numbers. If the number to the left is greater than or equal to the number to the right, it returns <code>true</code>. Otherwise, it returns <code>false</code>.
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Like the equality operator, <code>greater than or equal to</code> operator will convert data types while comparing.
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<strong>Examples</strong>
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<blockquote> 6 >= 6 // true<br> 7 >= '3' // true<br> 2 >= 3 // false<br>'7' >= 9 // false</blockquote>
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```js
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6 >= 6 // true
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7 >= '3' // true
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2 >= 3 // false
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'7' >= 9 // false
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```
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|
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</section>
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|
||||
## Instructions
|
||||
|
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@@ -9,7 +9,15 @@ videoUrl: 'https://scrimba.com/c/cdBm9Sr'
|
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<section id='description'>
|
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The inequality operator (<code>!=</code>) is the opposite of the equality operator. It means "Not Equal" and returns <code>false</code> where equality would return <code>true</code> and <em>vice versa</em>. Like the equality operator, the inequality operator will convert data types of values while comparing.
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<strong>Examples</strong>
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<blockquote>1 != 2 // true<br>1 != "1" // false<br>1 != '1' // false<br>1 != true // false<br>0 != false // false</blockquote>
|
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|
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```js
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1 != 2 // true
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1 != "1" // false
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1 != '1' // false
|
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1 != true // false
|
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0 != false // false
|
||||
```
|
||||
|
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</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,15 @@ videoUrl: 'https://scrimba.com/c/cNVRWtB'
|
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<section id='description'>
|
||||
The <dfn>less than</dfn> operator (<code><</code>) compares the values of two numbers. If the number to the left is less than the number to the right, it returns <code>true</code>. Otherwise, it returns <code>false</code>. Like the equality operator, <dfn>less than</dfn> operator converts data types while comparing.
|
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<strong>Examples</strong>
|
||||
<blockquote>2 < 5 // true<br>'3' < 7 // true<br>5 < 5 // false<br>3 < 2 // false<br>'8' < 4 // false</blockquote>
|
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|
||||
```js
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2 < 5 // true
|
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'3' < 7 // true
|
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5 < 5 // false
|
||||
3 < 2 // false
|
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'8' < 4 // false
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,15 @@ videoUrl: 'https://scrimba.com/c/cNVR7Am'
|
||||
<section id='description'>
|
||||
The <code>less than or equal to</code> operator (<code><=</code>) compares the values of two numbers. If the number to the left is less than or equal to the number to the right, it returns <code>true</code>. If the number on the left is greater than the number on the right, it returns <code>false</code>. Like the equality operator, <code>less than or equal to</code> converts data types.
|
||||
<strong>Examples</strong>
|
||||
<blockquote>4 <= 5 // true<br>'7' <= 7 // true<br>5 <= 5 // true<br>3 <= 2 // false<br>'8' <= 4 // false</blockquote>
|
||||
|
||||
```js
|
||||
4 <= 5 // true
|
||||
'7' <= 7 // true
|
||||
5 <= 5 // true
|
||||
3 <= 2 // false
|
||||
'8' <= 4 // false
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -10,7 +10,12 @@ videoUrl: 'https://scrimba.com/c/cy87atr'
|
||||
Strict equality (<code>===</code>) is the counterpart to the equality operator (<code>==</code>). However, unlike the equality operator, which attempts to convert both values being compared to a common type, the strict equality operator does not perform a type conversion.
|
||||
If the values being compared have different types, they are considered unequal, and the strict equality operator will return false.
|
||||
<strong>Examples</strong>
|
||||
<blockquote>3 === 3 // true<br>3 === '3' // false</blockquote>
|
||||
|
||||
```js
|
||||
3 === 3 // true
|
||||
3 === '3' // false
|
||||
```
|
||||
|
||||
In the second example, <code>3</code> is a <code>Number</code> type and <code>'3'</code> is a <code>String</code> type.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,13 @@ videoUrl: 'https://scrimba.com/c/cKekkUy'
|
||||
<section id='description'>
|
||||
The strict inequality operator (<code>!==</code>) is the logical opposite of the strict equality operator. It means "Strictly Not Equal" and returns <code>false</code> where strict equality would return <code>true</code> and <em>vice versa</em>. Strict inequality will not convert data types.
|
||||
<strong>Examples</strong>
|
||||
<blockquote>3 !== 3 // false<br>3 !== '3' // true<br>4 !== 3 // true</blockquote>
|
||||
|
||||
```js
|
||||
3 !== 3 // false
|
||||
3 !== '3' // true
|
||||
4 !== 3 // true
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,9 +9,25 @@ videoUrl: 'https://scrimba.com/c/cvbRVtr'
|
||||
<section id='description'>
|
||||
Sometimes you will need to test more than one thing at a time. The <dfn>logical and</dfn> operator (<code>&&</code>) returns <code>true</code> if and only if the <dfn>operands</dfn> to the left and right of it are true.
|
||||
The same effect could be achieved by nesting an if statement inside another if:
|
||||
<blockquote>if (num > 5) {<br> if (num < 10) {<br> return "Yes";<br> }<br>}<br>return "No";</blockquote>
|
||||
|
||||
```js
|
||||
if (num > 5) {
|
||||
if (num < 10) {
|
||||
return "Yes";
|
||||
}
|
||||
}
|
||||
return "No";
|
||||
```
|
||||
|
||||
will only return "Yes" if <code>num</code> is greater than <code>5</code> and less than <code>10</code>. The same logic can be written as:
|
||||
<blockquote>if (num > 5 && num < 10) {<br> return "Yes";<br>}<br>return "No";</blockquote>
|
||||
|
||||
```js
|
||||
if (num > 5 && num < 10) {
|
||||
return "Yes";
|
||||
}
|
||||
return "No";
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -10,9 +10,26 @@ videoUrl: 'https://scrimba.com/c/cEPrGTN'
|
||||
The <dfn>logical or</dfn> operator (<code>||</code>) returns <code>true</code> if either of the <dfn>operands</dfn> is <code>true</code>. Otherwise, it returns <code>false</code>.
|
||||
The <dfn>logical or</dfn> operator is composed of two pipe symbols (<code>|</code>). This can typically be found between your Backspace and Enter keys.
|
||||
The pattern below should look familiar from prior waypoints:
|
||||
<blockquote>if (num > 10) {<br> return "No";<br>}<br>if (num < 5) {<br> return "No";<br>}<br>return "Yes";</blockquote>
|
||||
|
||||
```js
|
||||
if (num > 10) {
|
||||
return "No";
|
||||
}
|
||||
if (num < 5) {
|
||||
return "No";
|
||||
}
|
||||
return "Yes";
|
||||
```
|
||||
|
||||
will return "Yes" only if <code>num</code> is between <code>5</code> and <code>10</code> (5 and 10 included). The same logic can be written as:
|
||||
<blockquote>if (num > 10 || num < 5) {<br> return "No";<br>}<br>return "Yes";</blockquote>
|
||||
|
||||
```js
|
||||
if (num > 10 || num < 5) {
|
||||
return "No";
|
||||
}
|
||||
return "Yes";
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -11,7 +11,13 @@ In programming, it is common to use assignments to modify the contents of a vari
|
||||
<code>myVar = myVar + 5;</code>
|
||||
to add <code>5</code> to <code>myVar</code>. Since this is such a common pattern, there are operators which do both a mathematical operation and assignment in one step.
|
||||
One such operator is the <code>+=</code> operator.
|
||||
<blockquote>var myVar = 1;<br>myVar += 5;<br>console.log(myVar); // Returns 6</blockquote>
|
||||
|
||||
```js
|
||||
var myVar = 1;
|
||||
myVar += 5;
|
||||
console.log(myVar); // Returns 6
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,11 @@ videoUrl: 'https://scrimba.com/c/cNpM8AN'
|
||||
<section id='description'>
|
||||
In JavaScript, when the <code>+</code> operator is used with a <code>String</code> value, it is called the <dfn>concatenation</dfn> operator. You can build a new string out of other strings by <dfn>concatenating</dfn> them together.
|
||||
<strong>Example</strong>
|
||||
<blockquote>'My name is Alan,' + ' I concatenate.'</blockquote>
|
||||
|
||||
```js
|
||||
'My name is Alan,' + ' I concatenate.'
|
||||
```
|
||||
|
||||
<strong>Note</strong><br>Watch out for spaces. Concatenation does not add spaces between concatenated strings, so you'll need to add them yourself.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -10,7 +10,14 @@ videoUrl: 'https://scrimba.com/c/c2R6BHa'
|
||||
A for loop can also count backwards, so long as we can define the right conditions.
|
||||
In order to count backwards by twos, we'll need to change our <code>initialization</code>, <code>condition</code>, and <code>final-expression</code>.
|
||||
We'll start at <code>i = 10</code> and loop while <code>i > 0</code>. We'll decrement <code>i</code> by 2 each loop with <code>i -= 2</code>.
|
||||
<blockquote>var ourArray = [];<br>for (var i=10; i > 0; i-=2) {<br> ourArray.push(i);<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [];
|
||||
for (var i=10; i > 0; i-=2) {
|
||||
ourArray.push(i);
|
||||
}
|
||||
```
|
||||
|
||||
<code>ourArray</code> will now contain <code>[10,8,6,4,2]</code>.
|
||||
Let's change our <code>initialization</code> and <code>final-expression</code> so we can count backward by twos by odd numbers.
|
||||
</section>
|
||||
|
||||
@@ -12,7 +12,11 @@ For example, computers distinguish between numbers, such as the number <code>12<
|
||||
<dfn>Variables</dfn> allow computers to store and manipulate data in a dynamic fashion. They do this by using a "label" to point to the data rather than using the data itself. Any of the seven data types may be stored in a variable.
|
||||
<code>Variables</code> are similar to the x and y variables you use in mathematics, which means they're a simple name to represent the data we want to refer to. Computer <code>variables</code> differ from mathematical variables in that they can store different values at different times.
|
||||
We tell JavaScript to create or <dfn>declare</dfn> a variable by putting the keyword <code>var</code> in front of it, like so:
|
||||
<blockquote>var ourName;</blockquote>
|
||||
|
||||
```js
|
||||
var ourName;
|
||||
```
|
||||
|
||||
creates a <code>variable</code> called <code>ourName</code>. In JavaScript we end statements with semicolons.
|
||||
<code>Variable</code> names can be made up of numbers, letters, and <code>$</code> or <code>_</code>, but may not contain spaces or start with a number.
|
||||
</section>
|
||||
|
||||
@@ -11,7 +11,11 @@ We can also divide one number by another.
|
||||
JavaScript uses the <code>/</code> symbol for division.
|
||||
|
||||
<strong>Example</strong>
|
||||
<blockquote>myVar = 16 / 2; // assigned 8</blockquote>
|
||||
|
||||
```js
|
||||
myVar = 16 / 2; // assigned 8
|
||||
```
|
||||
|
||||
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,15 @@ videoUrl: 'https://scrimba.com/c/c2QwKH2'
|
||||
<section id='description'>
|
||||
It is possible to have both <dfn>local</dfn> and <dfn>global</dfn> variables with the same name. When you do this, the <code>local</code> variable takes precedence over the <code>global</code> variable.
|
||||
In this example:
|
||||
<blockquote>var someVar = "Hat";<br>function myFun() {<br> var someVar = "Head";<br> return someVar;<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var someVar = "Hat";
|
||||
function myFun() {
|
||||
var someVar = "Head";
|
||||
return someVar;
|
||||
}
|
||||
```
|
||||
|
||||
The function <code>myFun</code> will return <code>"Head"</code> because the <code>local</code> version of the variable is present.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -8,7 +8,17 @@ videoUrl: 'https://scrimba.com/c/caeJ2hm'
|
||||
## Description
|
||||
<section id='description'>
|
||||
If you have multiple conditions that need to be addressed, you can chain <code>if</code> statements together with <code>else if</code> statements.
|
||||
<blockquote>if (num > 15) {<br> return "Bigger than 15";<br>} else if (num < 5) {<br> return "Smaller than 5";<br>} else {<br> return "Between 5 and 15";<br>}</blockquote>
|
||||
|
||||
```js
|
||||
if (num > 15) {
|
||||
return "Bigger than 15";
|
||||
} else if (num < 5) {
|
||||
return "Smaller than 5";
|
||||
} else {
|
||||
return "Between 5 and 15";
|
||||
}
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -8,7 +8,15 @@ videoUrl: 'https://scrimba.com/c/cek4Efq'
|
||||
## Description
|
||||
<section id='description'>
|
||||
When a condition for an <code>if</code> statement is true, the block of code following it is executed. What about when that condition is false? Normally nothing would happen. With an <code>else</code> statement, an alternate block of code can be executed.
|
||||
<blockquote>if (num > 10) {<br> return "Bigger than 10";<br>} else {<br> return "10 or Less";<br>}</blockquote>
|
||||
|
||||
```js
|
||||
if (num > 10) {
|
||||
return "Bigger than 10";
|
||||
} else {
|
||||
return "10 or Less";
|
||||
}
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,14 @@ videoUrl: 'https://scrimba.com/c/cm8n7T9'
|
||||
<section id='description'>
|
||||
For loops don't have to iterate one at a time. By changing our <code>final-expression</code>, we can count by even numbers.
|
||||
We'll start at <code>i = 0</code> and loop while <code>i < 10</code>. We'll increment <code>i</code> by 2 each loop with <code>i += 2</code>.
|
||||
<blockquote>var ourArray = [];<br>for (var i = 0; i < 10; i += 2) {<br> ourArray.push(i);<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [];
|
||||
for (var i = 0; i < 10; i += 2) {
|
||||
ourArray.push(i);
|
||||
}
|
||||
```
|
||||
|
||||
<code>ourArray</code> will now contain <code>[0,2,4,6,8]</code>.
|
||||
Let's change our <code>initialization</code> so we can count by odd numbers.
|
||||
</section>
|
||||
|
||||
@@ -8,7 +8,14 @@ videoUrl: 'https://scrimba.com/c/caeR3HB'
|
||||
## Description
|
||||
<section id='description'>
|
||||
A common task in JavaScript is to iterate through the contents of an array. One way to do that is with a <code>for</code> loop. This code will output each element of the array <code>arr</code> to the console:
|
||||
<blockquote>var arr = [10,9,8,7,6];<br>for (var i = 0; i < arr.length; i++) {<br> console.log(arr[i]);<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var arr = [10,9,8,7,6];
|
||||
for (var i = 0; i < arr.length; i++) {
|
||||
console.log(arr[i]);
|
||||
}
|
||||
```
|
||||
|
||||
Remember that Arrays have zero-based numbering, which means the last index of the array is length - 1. Our <dfn>condition</dfn> for this loop is <code>i < arr.length</code>, which stops when <code>i</code> is at length - 1.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -8,13 +8,40 @@ videoUrl: 'https://scrimba.com/c/cDqWGcp'
|
||||
## Description
|
||||
<section id='description'>
|
||||
The next type of loop you will learn is called a <code>do...while</code> loop. It is called a <code>do...while</code> loop because it will first <code>do</code> one pass of the code inside the loop no matter what, and then continue to run the loop <code>while</code> the specified condition evaluates to <code>true</code>.
|
||||
<blockquote>var ourArray = [];<br>var i = 0;<br>do {<br> ourArray.push(i);<br> i++;<br>} while (i < 5);</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [];
|
||||
var i = 0;
|
||||
do {
|
||||
ourArray.push(i);
|
||||
i++;
|
||||
} while (i < 5);
|
||||
```
|
||||
|
||||
The example above behaves similar to other types of loops, and the resulting array will look like <code>[0, 1, 2, 3, 4]</code>. However, what makes the <code>do...while</code> different from other loops is how it behaves when the condition fails on the first check. Let's see this in action:
|
||||
Here is a regular <code>while</code> loop that will run the code in the loop as long as <code>i < 5</code>:
|
||||
<blockquote>var ourArray = []; <br>var i = 5;<br>while (i < 5) {<br> ourArray.push(i);<br> i++;<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [];
|
||||
var i = 5;
|
||||
while (i < 5) {
|
||||
ourArray.push(i);
|
||||
i++;
|
||||
}
|
||||
```
|
||||
|
||||
In this example, we initialize the value of <code>myArray</code> to an empty array and the value of <code>i</code> to 5. When we execute the <code>while</code> loop, the condition evaluates to <code>false</code> because <code>i</code> is not less than 5, so we do not execute the code inside the loop. The result is that <code>ourArray</code> will end up with no values added to it, and it will still look like <code>[]</code> when all of the code in the example above has completed running.
|
||||
Now, take a look at a <code>do...while</code> loop:
|
||||
<blockquote>var ourArray = []; <br>var i = 5;<br>do {<br> ourArray.push(i);<br> i++;<br>} while (i < 5);</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [];
|
||||
var i = 5;
|
||||
do {
|
||||
ourArray.push(i);
|
||||
i++;
|
||||
} while (i < 5);
|
||||
```
|
||||
|
||||
In this case, we initialize the value of <code>i</code> to 5, just like we did with the <code>while</code> loop. When we get to the next line, there is no condition to evaluate, so we go to the code inside the curly braces and execute it. We will add a single element to the array and then increment <code>i</code> before we get to the condition check. When we finally evaluate the condition <code>i < 5</code> on the last line, we see that <code>i</code> is now 6, which fails the conditional check, so we exit the loop and are done. At the end of the above example, the value of <code>ourArray</code> is <code>[5]</code>.
|
||||
Essentially, a <code>do...while</code> loop ensures that the code inside the loop will run at least once.
|
||||
Let's try getting a <code>do...while</code> loop to work by pushing values to an array.
|
||||
|
||||
@@ -15,7 +15,14 @@ The <code>initialization</code> statement is executed one time only before the l
|
||||
The <code>condition</code> statement is evaluated at the beginning of every loop iteration and will continue as long as it evaluates to <code>true</code>. When <code>condition</code> is <code>false</code> at the start of the iteration, the loop will stop executing. This means if <code>condition</code> starts as <code>false</code>, your loop will never execute.
|
||||
The <code>final-expression</code> is executed at the end of each loop iteration, prior to the next <code>condition</code> check and is usually used to increment or decrement your loop counter.
|
||||
In the following example we initialize with <code>i = 0</code> and iterate while our condition <code>i < 5</code> is true. We'll increment <code>i</code> by <code>1</code> in each loop iteration with <code>i++</code> as our <code>final-expression</code>.
|
||||
<blockquote>var ourArray = [];<br>for (var i = 0; i < 5; i++) {<br> ourArray.push(i);<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [];
|
||||
for (var i = 0; i < 5; i++) {
|
||||
ourArray.push(i);
|
||||
}
|
||||
```
|
||||
|
||||
<code>ourArray</code> will now contain <code>[0,1,2,3,4]</code>.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,16 @@ videoUrl: 'https://scrimba.com/c/c8QbnCM'
|
||||
<section id='description'>
|
||||
You can run the same code multiple times by using a loop.
|
||||
The first type of loop we will learn is called a <code>while</code> loop because it runs "while" a specified condition is true and stops once that condition is no longer true.
|
||||
<blockquote>var ourArray = [];<br>var i = 0;<br>while(i < 5) {<br> ourArray.push(i);<br> i++;<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [];
|
||||
var i = 0;
|
||||
while(i < 5) {
|
||||
ourArray.push(i);
|
||||
i++;
|
||||
}
|
||||
```
|
||||
|
||||
Let's try getting a while loop to work by pushing values to an array.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,16 @@ videoUrl: 'https://scrimba.com/c/cd62NhM'
|
||||
<section id='description'>
|
||||
Variables which are declared within a function, as well as the function parameters have <dfn>local</dfn> scope. That means, they are only visible within that function.
|
||||
Here is a function <code>myTest</code> with a local variable called <code>loc</code>.
|
||||
<blockquote>function myTest() {<br> var loc = "foo";<br> console.log(loc);<br>}<br>myTest(); // logs "foo"<br>console.log(loc); // loc is not defined</blockquote>
|
||||
|
||||
```js
|
||||
function myTest() {
|
||||
var loc = "foo";
|
||||
console.log(loc);
|
||||
}
|
||||
myTest(); // logs "foo"
|
||||
console.log(loc); // loc is not defined
|
||||
```
|
||||
|
||||
<code>loc</code> is not defined outside of the function.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -11,11 +11,40 @@ Order is important in <code>if</code>, <code>else if</code> statements.
|
||||
The function is executed from top to bottom so you will want to be careful of what statement comes first.
|
||||
Take these two functions as an example.
|
||||
Here's the first:
|
||||
<blockquote>function foo(x) {<br> if (x < 1) {<br> return "Less than one";<br> } else if (x < 2) {<br> return "Less than two";<br> } else {<br> return "Greater than or equal to two";<br> }<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function foo(x) {
|
||||
if (x < 1) {
|
||||
return "Less than one";
|
||||
} else if (x < 2) {
|
||||
return "Less than two";
|
||||
} else {
|
||||
return "Greater than or equal to two";
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
And the second just switches the order of the statements:
|
||||
<blockquote>function bar(x) {<br> if (x < 2) {<br> return "Less than two";<br> } else if (x < 1) {<br> return "Less than one";<br> } else {<br> return "Greater than or equal to two";<br> }<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function bar(x) {
|
||||
if (x < 2) {
|
||||
return "Less than two";
|
||||
} else if (x < 1) {
|
||||
return "Less than one";
|
||||
} else {
|
||||
return "Greater than or equal to two";
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
While these two functions look nearly identical if we pass a number to both we get different outputs.
|
||||
<blockquote>foo(0) // "Less than one"<br>bar(0) // "Less than two"</blockquote>
|
||||
|
||||
```js
|
||||
foo(0) // "Less than one"
|
||||
bar(0) // "Less than two"
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -10,7 +10,14 @@ videoUrl: 'https://scrimba.com/c/cRbVZAB'
|
||||
Another way to change the data in an array is with the <code>.pop()</code> function.
|
||||
<code>.pop()</code> is used to "pop" a value off of the end of an array. We can store this "popped off" value by assigning it to a variable. In other words, <code>.pop()</code> removes the last element from an array and returns that element.
|
||||
Any type of entry can be "popped" off of an array - numbers, strings, even nested arrays.
|
||||
<blockquote><code>var threeArr = [1, 4, 6];<br> var oneDown = threeArr.pop();<br> console.log(oneDown); // Returns 6<br> console.log(threeArr); // Returns [1, 4]</code></blockquote>
|
||||
|
||||
```js
|
||||
var threeArr = [1, 4, 6];
|
||||
var oneDown = threeArr.pop();
|
||||
console.log(oneDown); // Returns 6
|
||||
console.log(threeArr); // Returns [1, 4]
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,13 @@ videoUrl: 'https://scrimba.com/c/cnqmVtJ'
|
||||
<section id='description'>
|
||||
An easy way to append data to the end of an array is via the <code>push()</code> function.
|
||||
<code>.push()</code> takes one or more <dfn>parameters</dfn> and "pushes" them onto the end of the array.
|
||||
<blockquote>var arr = [1,2,3];<br>arr.push(4);<br>// arr is now [1,2,3,4]</blockquote>
|
||||
|
||||
```js
|
||||
var arr = [1,2,3];
|
||||
arr.push(4);
|
||||
// arr is now [1,2,3,4]
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,11 +9,41 @@ videoUrl: 'https://scrimba.com/c/c9yNMfR'
|
||||
<section id='description'>
|
||||
Sometimes you may want to store data in a flexible <dfn>Data Structure</dfn>. A JavaScript object is one way to handle flexible data. They allow for arbitrary combinations of <dfn>strings</dfn>, <dfn>numbers</dfn>, <dfn>booleans</dfn>, <dfn>arrays</dfn>, <dfn>functions</dfn>, and <dfn>objects</dfn>.
|
||||
Here's an example of a complex data structure:
|
||||
<blockquote>var ourMusic = [<br> {<br> "artist": "Daft Punk",<br> "title": "Homework",<br> "release_year": 1997,<br> "formats": [ <br> "CD", <br> "Cassette", <br> "LP"<br> ],<br> "gold": true<br> }<br>];</blockquote>
|
||||
|
||||
```js
|
||||
var ourMusic = [
|
||||
{
|
||||
"artist": "Daft Punk",
|
||||
"title": "Homework",
|
||||
"release_year": 1997,
|
||||
"formats": [
|
||||
"CD",
|
||||
"Cassette",
|
||||
"LP"
|
||||
],
|
||||
"gold": true
|
||||
}
|
||||
];
|
||||
```
|
||||
|
||||
This is an array which contains one object inside. The object has various pieces of <dfn>metadata</dfn> about an album. It also has a nested <code>"formats"</code> array. If you want to add more album records, you can do this by adding records to the top level array.
|
||||
Objects hold data in a property, which has a key-value format. In the example above, <code>"artist": "Daft Punk"</code> is a property that has a key of <code>"artist"</code> and a value of <code>"Daft Punk"</code>.
|
||||
<a href='http://www.json.org/' target=_blank>JavaScript Object Notation</a> or <code>JSON</code> is a related data interchange format used to store data.
|
||||
<blockquote>{<br> "artist": "Daft Punk",<br> "title": "Homework",<br> "release_year": 1997,<br> "formats": [ <br> "CD",<br> "Cassette",<br> "LP"<br> ],<br> "gold": true<br>}</blockquote>
|
||||
|
||||
```json
|
||||
{
|
||||
"artist": "Daft Punk",
|
||||
"title": "Homework",
|
||||
"release_year": 1997,
|
||||
"formats": [
|
||||
"CD",
|
||||
"Cassette",
|
||||
"LP"
|
||||
],
|
||||
"gold": true
|
||||
}
|
||||
```
|
||||
|
||||
<strong>Note</strong><br>You will need to place a comma after every object in the array, unless it is the last object in the array.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,12 @@ videoUrl: 'https://scrimba.com/c/czQM4A8'
|
||||
<section id='description'>
|
||||
Unlike strings, the entries of arrays are <dfn>mutable</dfn> and can be changed freely.
|
||||
<strong>Example</strong>
|
||||
<blockquote>var ourArray = [50,40,30];<br>ourArray[0] = 15; // equals [15,40,30]</blockquote>
|
||||
|
||||
```js
|
||||
var ourArray = [50,40,30];
|
||||
ourArray[0] = 15; // equals [15,40,30]
|
||||
```
|
||||
|
||||
<strong>Note</strong><br>There shouldn't be any spaces between the array name and the square brackets, like <code>array [0]</code>. Although JavaScript is able to process this correctly, this may confuse other programmers reading your code.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -8,7 +8,19 @@ videoUrl: 'https://scrimba.com/c/cdBKWCV'
|
||||
## Description
|
||||
<section id='description'>
|
||||
If the <code>break</code> statement is omitted from a <code>switch</code> statement's <code>case</code>, the following <code>case</code> statement(s) are executed until a <code>break</code> is encountered. If you have multiple inputs with the same output, you can represent them in a <code>switch</code> statement like this:
|
||||
<blockquote>switch(val) {<br> case 1:<br> case 2:<br> case 3:<br> result = "1, 2, or 3";<br> break;<br> case 4:<br> result = "4 alone";<br>}</blockquote>
|
||||
|
||||
```js
|
||||
switch(val) {
|
||||
case 1:
|
||||
case 2:
|
||||
case 3:
|
||||
result = "1, 2, or 3";
|
||||
break;
|
||||
case 4:
|
||||
result = "4 alone";
|
||||
}
|
||||
```
|
||||
|
||||
Cases for 1, 2, and 3 will all produce the same result.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -11,7 +11,11 @@ We can also multiply one number by another.
|
||||
JavaScript uses the <code>*</code> symbol for multiplication of two numbers.
|
||||
|
||||
<strong>Example</strong>
|
||||
<blockquote>myVar = 13 * 13; // assigned 169</blockquote>
|
||||
|
||||
```js
|
||||
myVar = 13 * 13; // assigned 169
|
||||
```
|
||||
|
||||
|
||||
</section>
|
||||
|
||||
|
||||
@@ -8,7 +8,18 @@ videoUrl: 'https://scrimba.com/c/cRn6GHM'
|
||||
## Description
|
||||
<section id='description'>
|
||||
If you have a multi-dimensional array, you can use the same logic as the prior waypoint to loop through both the array and any sub-arrays. Here is an example:
|
||||
<blockquote>var arr = [<br> [1,2], [3,4], [5,6]<br>];<br>for (var i=0; i < arr.length; i++) {<br> for (var j=0; j < arr[i].length; j++) {<br> console.log(arr[i][j]);<br> }<br>}</blockquote>
|
||||
|
||||
```js
|
||||
var arr = [
|
||||
[1,2], [3,4], [5,6]
|
||||
];
|
||||
for (var i=0; i < arr.length; i++) {
|
||||
for (var j=0; j < arr[i].length; j++) {
|
||||
console.log(arr[i][j]);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
This outputs each sub-element in <code>arr</code> one at a time. Note that for the inner loop, we are checking the <code>.length</code> of <code>arr[i]</code>, since <code>arr[i]</code> is itself an array.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,13 @@ videoUrl: 'https://scrimba.com/c/cy8rahW'
|
||||
<section id='description'>
|
||||
<dfn>Parameters</dfn> are variables that act as placeholders for the values that are to be input to a function when it is called. When a function is defined, it is typically defined along with one or more parameters. The actual values that are input (or <dfn>"passed"</dfn>) into a function when it is called are known as <dfn>arguments</dfn>.
|
||||
Here is a function with two parameters, <code>param1</code> and <code>param2</code>:
|
||||
<blockquote>function testFun(param1, param2) {<br> console.log(param1, param2);<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function testFun(param1, param2) {
|
||||
console.log(param1, param2);
|
||||
}
|
||||
```
|
||||
|
||||
Then we can call <code>testFun</code>:
|
||||
<code>testFun("Hello", "World");</code>
|
||||
We have passed two arguments, <code>"Hello"</code> and <code>"World"</code>. Inside the function, <code>param1</code> will equal "Hello" and <code>param2</code> will equal "World". Note that you could call <code>testFun</code> again with different arguments and the parameters would take on the value of the new arguments.
|
||||
|
||||
@@ -10,9 +10,19 @@ videoUrl: 'https://scrimba.com/c/cm8PqCa'
|
||||
In the last two challenges, we learned about the equality operator (<code>==</code>) and the strict equality operator (<code>===</code>). Let's do a quick review and practice using these operators some more.
|
||||
If the values being compared are not of the same type, the equality operator will perform a type conversion, and then evaluate the values. However, the strict equality operator will compare both the data type and value as-is, without converting one type to the other.
|
||||
<strong>Examples</strong>
|
||||
<blockquote>3 == '3' // returns true because JavaScript performs type conversion from string to number<br>3 === '3' // returns false because the types are different and type conversion is not performed</blockquote>
|
||||
|
||||
```js
|
||||
3 == '3' // returns true because JavaScript performs type conversion from string to number
|
||||
3 === '3' // returns false because the types are different and type conversion is not performed
|
||||
```
|
||||
|
||||
<strong>Note</strong><br>In JavaScript, you can determine the type of a variable or a value with the <code>typeof</code> operator, as follows:
|
||||
<blockquote>typeof 3 // returns 'number'<br>typeof '3' // returns 'string'</blockquote>
|
||||
|
||||
```js
|
||||
typeof 3 // returns 'number'
|
||||
typeof '3' // returns 'string'
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -8,11 +8,25 @@ videoUrl: 'https://scrimba.com/c/cbQmnhM'
|
||||
## Description
|
||||
<section id='description'>
|
||||
<dfn>String</dfn> values in JavaScript may be written with single or double quotes, as long as you start and end with the same type of quote. Unlike some other programming languages, single and double quotes work the same in JavaScript.
|
||||
<blockquote>doubleQuoteStr = "This is a string"; <br/>singleQuoteStr = 'This is also a string';</blockquote>
|
||||
|
||||
```js
|
||||
doubleQuoteStr = "This is a string";
|
||||
singleQuoteStr = 'This is also a string';
|
||||
```
|
||||
|
||||
The reason why you might want to use one type of quote over the other is if you want to use both in a string. This might happen if you want to save a conversation in a string and have the conversation in quotes. Another use for it would be saving an <code><a></code> tag with various attributes in quotes, all within a string.
|
||||
<blockquote>conversation = 'Finn exclaims to Jake, "Algebraic!"';</blockquote>
|
||||
|
||||
```js
|
||||
conversation = 'Finn exclaims to Jake, "Algebraic!"';
|
||||
```
|
||||
|
||||
However, this becomes a problem if you need to use the outermost quotes within it. Remember, a string has the same kind of quote at the beginning and end. But if you have that same quote somewhere in the middle, the string will stop early and throw an error.
|
||||
<blockquote>goodStr = 'Jake asks Finn, "Hey, let\'s go on an adventure?"'; <br/>badStr = 'Finn responds, "Let's go!"'; // Throws an error</blockquote>
|
||||
|
||||
```js
|
||||
goodStr = 'Jake asks Finn, "Hey, let\'s go on an adventure?"';
|
||||
badStr = 'Finn responds, "Let's go!"'; // Throws an error
|
||||
```
|
||||
|
||||
In the <dfn>goodStr</dfn> above, you can use both quotes safely by using the backslash <code>\</code> as an escape character.
|
||||
<strong>Note</strong><br/>The backslash <code>\</code> should not be confused with the forward slash <code>/</code>. They do not do the same thing.
|
||||
</section>
|
||||
|
||||
@@ -8,9 +8,32 @@ videoUrl: 'https://scrimba.com/c/c3JE8fy'
|
||||
## Description
|
||||
<section id='description'>
|
||||
If you have many options to choose from, a <code>switch</code> statement can be easier to write than many chained <code>if</code>/<code>else if</code> statements. The following:
|
||||
<blockquote>if (val === 1) {<br> answer = "a";<br>} else if (val === 2) {<br> answer = "b";<br>} else {<br> answer = "c";<br>}</blockquote>
|
||||
|
||||
```js
|
||||
if (val === 1) {
|
||||
answer = "a";
|
||||
} else if (val === 2) {
|
||||
answer = "b";
|
||||
} else {
|
||||
answer = "c";
|
||||
}
|
||||
```
|
||||
|
||||
can be replaced with:
|
||||
<blockquote>switch(val) {<br> case 1:<br> answer = "a";<br> break;<br> case 2:<br> answer = "b";<br> break;<br> default:<br> answer = "c";<br>}</blockquote>
|
||||
|
||||
```js
|
||||
switch(val) {
|
||||
case 1:
|
||||
answer = "a";
|
||||
break;
|
||||
case 2:
|
||||
answer = "b";
|
||||
break;
|
||||
default:
|
||||
answer = "c";
|
||||
}
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,14 @@ videoUrl: 'https://scrimba.com/c/cy87wue'
|
||||
<section id='description'>
|
||||
We can pass values into a function with <dfn>arguments</dfn>. You can use a <code>return</code> statement to send a value back out of a function.
|
||||
<strong>Example</strong>
|
||||
<blockquote>function plusThree(num) {<br> return num + 3;<br>}<br>var answer = plusThree(5); // 8</blockquote>
|
||||
|
||||
```js
|
||||
function plusThree(num) {
|
||||
return num + 3;
|
||||
}
|
||||
var answer = plusThree(5); // 8
|
||||
```
|
||||
|
||||
<code>plusThree</code> takes an <dfn>argument</dfn> for <code>num</code> and returns a value equal to <code>num + 3</code>.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,16 @@ videoUrl: 'https://scrimba.com/c/cQe39Sq'
|
||||
<section id='description'>
|
||||
When a <code>return</code> statement is reached, the execution of the current function stops and control returns to the calling location.
|
||||
<strong>Example</strong>
|
||||
<blockquote>function myFun() {<br> console.log("Hello");<br> return "World";<br> console.log("byebye")<br>}<br>myFun();</blockquote>
|
||||
|
||||
```js
|
||||
function myFun() {
|
||||
console.log("Hello");
|
||||
return "World";
|
||||
console.log("byebye")
|
||||
}
|
||||
myFun();
|
||||
```
|
||||
|
||||
The above outputs "Hello" to the console, returns "World", but <code>"byebye"</code> is never output, because the function exits at the <code>return</code> statement.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,9 +9,25 @@ videoUrl: 'https://scrimba.com/c/cp62qAQ'
|
||||
<section id='description'>
|
||||
You may recall from <a href="learn/javascript-algorithms-and-data-structures/basic-javascript/comparison-with-the-equality-operator" target="_blank">Comparison with the Equality Operator</a> that all comparison operators return a boolean <code>true</code> or <code>false</code> value.
|
||||
Sometimes people use an if/else statement to do a comparison, like this:
|
||||
<blockquote>function isEqual(a,b) {<br> if (a === b) {<br> return true;<br> } else {<br> return false;<br> }<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function isEqual(a,b) {
|
||||
if (a === b) {
|
||||
return true;
|
||||
} else {
|
||||
return false;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
But there's a better way to do this. Since <code>===</code> returns <code>true</code> or <code>false</code>, we can return the result of the comparison:
|
||||
<blockquote>function isEqual(a,b) {<br> return a === b;<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function isEqual(a,b) {
|
||||
return a === b;
|
||||
}
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,22 @@ videoUrl: 'https://scrimba.com/c/c4mv4fm'
|
||||
<section id='description'>
|
||||
If you have many options to choose from, use a <code>switch</code> statement. A <code>switch</code> statement tests a value and can have many <code>case</code> statements which define various possible values. Statements are executed from the first matched <code>case</code> value until a <code>break</code> is encountered.
|
||||
Here is a <dfn>pseudocode</dfn> example:
|
||||
<blockquote>switch(num) {<br> case value1:<br> statement1;<br> break;<br> case value2:<br> statement2;<br> break;<br>...<br> case valueN:<br> statementN;<br> break;<br>}</blockquote>
|
||||
|
||||
```js
|
||||
switch(num) {
|
||||
case value1:
|
||||
statement1;
|
||||
break;
|
||||
case value2:
|
||||
statement2;
|
||||
break;
|
||||
...
|
||||
case valueN:
|
||||
statementN;
|
||||
break;
|
||||
}
|
||||
```
|
||||
|
||||
<code>case</code> values are tested with strict equality (<code>===</code>). The <code>break</code> tells JavaScript to stop executing statements. If the <code>break</code> is omitted, the next statement will be executed.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -11,7 +11,12 @@ In JavaScript, you can store a value in a variable with the <dfn>assignment</dfn
|
||||
<code>myVariable = 5;</code>
|
||||
This assigns the <code>Number</code> value <code>5</code> to <code>myVariable</code>.
|
||||
Assignment always goes from right to left. Everything to the right of the <code>=</code> operator is resolved before the value is assigned to the variable to the left of the operator.
|
||||
<blockquote>myVar = 5;<br>myNum = myVar;</blockquote>
|
||||
|
||||
```js
|
||||
myVar = 5;
|
||||
myNum = myVar;
|
||||
```
|
||||
|
||||
This assigns <code>5</code> to <code>myVar</code> and then resolves <code>myVar</code> to <code>5</code> again and assigns it to <code>myNum</code>.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -11,7 +11,11 @@ We can also subtract one number from another.
|
||||
JavaScript uses the <code>-</code> symbol for subtraction.
|
||||
|
||||
<strong>Example</strong>
|
||||
<blockquote>myVar = 12 - 6; // assigned 6</blockquote>
|
||||
|
||||
```js
|
||||
myVar = 12 - 6; // assigned 6
|
||||
```
|
||||
|
||||
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,16 @@ videoUrl: 'https://scrimba.com/c/cm8Q7Ua'
|
||||
<section id='description'>
|
||||
Sometimes it is useful to check if the property of a given object exists or not. We can use the <code>.hasOwnProperty(propname)</code> method of objects to determine if that object has the given property name. <code>.hasOwnProperty()</code> returns <code>true</code> or <code>false</code> if the property is found or not.
|
||||
<strong>Example</strong>
|
||||
<blockquote>var myObj = {<br> top: "hat",<br> bottom: "pants"<br>};<br>myObj.hasOwnProperty("top"); // true<br>myObj.hasOwnProperty("middle"); // false</blockquote>
|
||||
|
||||
```js
|
||||
var myObj = {
|
||||
top: "hat",
|
||||
bottom: "pants"
|
||||
};
|
||||
myObj.hasOwnProperty("top"); // true
|
||||
myObj.hasOwnProperty("middle"); // false
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,9 +9,19 @@ videoUrl: 'https://scrimba.com/c/cWPVaUR'
|
||||
<section id='description'>
|
||||
In JavaScript, <code>String</code> values are <dfn>immutable</dfn>, which means that they cannot be altered once created.
|
||||
For example, the following code:
|
||||
<blockquote>var myStr = "Bob";<br>myStr[0] = "J";</blockquote>
|
||||
|
||||
```js
|
||||
var myStr = "Bob";
|
||||
myStr[0] = "J";
|
||||
```
|
||||
|
||||
cannot change the value of <code>myStr</code> to "Job", because the contents of <code>myStr</code> cannot be altered. Note that this does <em>not</em> mean that <code>myStr</code> cannot be changed, just that the individual characters of a <dfn>string literal</dfn> cannot be changed. The only way to change <code>myStr</code> would be to assign it with a new string, like this:
|
||||
<blockquote>var myStr = "Bob";<br>myStr = "Job";</blockquote>
|
||||
|
||||
```js
|
||||
var myStr = "Bob";
|
||||
myStr = "Job";
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -12,7 +12,13 @@ In JavaScript all variables and function names are case sensitive. This means th
|
||||
<h4>Best Practice</h4>
|
||||
Write variable names in JavaScript in <dfn>camelCase</dfn>. In <dfn>camelCase</dfn>, multi-word variable names have the first word in lowercase and the first letter of each subsequent word is capitalized.
|
||||
<strong>Examples:</strong>
|
||||
<blockquote>var someVariable;<br>var anotherVariableName;<br>var thisVariableNameIsSoLong;</blockquote>
|
||||
|
||||
```js
|
||||
var someVariable;
|
||||
var anotherVariableName;
|
||||
var thisVariableNameIsSoLong;
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,15 @@ videoUrl: 'https://scrimba.com/c/ce2p7cL'
|
||||
<section id='description'>
|
||||
A function can include the <code>return</code> statement but it does not have to. In the case that the function doesn't have a <code>return</code> statement, when you call it, the function processes the inner code but the returned value is <code>undefined</code>.
|
||||
<strong>Example</strong>
|
||||
<blockquote>var sum = 0;<br>function addSum(num) {<br> sum = sum + num;<br>}<br>var returnedValue = addSum(3); // sum will be modified but returned value is undefined</blockquote>
|
||||
|
||||
```js
|
||||
var sum = 0;
|
||||
function addSum(num) {
|
||||
sum = sum + num;
|
||||
}
|
||||
var returnedValue = addSum(3); // sum will be modified but returned value is undefined
|
||||
```
|
||||
|
||||
<code>addSum</code> is a function without a <code>return</code> statement. The function will change the global <code>sum</code> variable but the returned value of the function is <code>undefined</code>.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,7 +9,16 @@ videoUrl: 'https://scrimba.com/c/c9yEJT4'
|
||||
<section id='description'>
|
||||
After you've created a JavaScript object, you can update its properties at any time just like you would update any other variable. You can use either dot or bracket notation to update.
|
||||
For example, let's look at <code>ourDog</code>:
|
||||
<blockquote>var ourDog = {<br> "name": "Camper",<br> "legs": 4,<br> "tails": 1,<br> "friends": ["everything!"]<br>};</blockquote>
|
||||
|
||||
```js
|
||||
var ourDog = {
|
||||
"name": "Camper",
|
||||
"legs": 4,
|
||||
"tails": 1,
|
||||
"friends": ["everything!"]
|
||||
};
|
||||
```
|
||||
|
||||
Since he's a particularly happy dog, let's change his name to "Happy Camper". Here's how we update his object's name property:
|
||||
<code>ourDog.name = "Happy Camper";</code> or
|
||||
<code>ourDog["name"] = "Happy Camper";</code>
|
||||
|
||||
@@ -12,7 +12,18 @@ When the condition evaluates to <code>true</code>, the program executes the stat
|
||||
<strong>Pseudocode</strong>
|
||||
<blockquote>if (<i>condition is true</i>) {<br> <i>statement is executed</i><br>}</blockquote>
|
||||
<strong>Example</strong>
|
||||
<blockquote>function test (myCondition) {<br> if (myCondition) {<br> return "It was true";<br> }<br> return "It was false";<br>}<br>test(true); // returns "It was true"<br>test(false); // returns "It was false"</blockquote>
|
||||
|
||||
```js
|
||||
function test (myCondition) {
|
||||
if (myCondition) {
|
||||
return "It was true";
|
||||
}
|
||||
return "It was false";
|
||||
}
|
||||
test(true); // returns "It was true"
|
||||
test(false); // returns "It was false"
|
||||
```
|
||||
|
||||
When <code>test</code> is called with a value of <code>true</code>, the <code>if</code> statement evaluates <code>myCondition</code> to see if it is <code>true</code> or not. Since it is <code>true</code>, the function returns <code>"It was true"</code>. When we call <code>test</code> with a value of <code>false</code>, <code>myCondition</code> is <em>not</em> <code>true</code> and the statement in the curly braces is not executed and the function returns <code>"It was false"</code>.
|
||||
</section>
|
||||
|
||||
|
||||
@@ -9,9 +9,29 @@ videoUrl: 'https://scrimba.com/c/cyWJBT4'
|
||||
<section id='description'>
|
||||
In the previous challenge, you used a single <code>conditional operator</code>. You can also chain them together to check for multiple conditions.
|
||||
The following function uses if, else if, and else statements to check multiple conditions:
|
||||
<blockquote>function findGreaterOrEqual(a, b) {<br> if (a === b) {<br> return "a and b are equal";<br> }<br> else if (a > b) {<br> return "a is greater";<br> }<br> else {<br> return "b is greater";<br> }<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function findGreaterOrEqual(a, b) {
|
||||
if (a === b) {
|
||||
return "a and b are equal";
|
||||
}
|
||||
else if (a > b) {
|
||||
return "a is greater";
|
||||
}
|
||||
else {
|
||||
return "b is greater";
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
The above function can be re-written using multiple <code>conditional operators</code>:
|
||||
<blockquote>function findGreaterOrEqual(a, b) {<br> return (a === b) ? "a and b are equal" : (a > b) ? "a is greater" : "b is greater";<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function findGreaterOrEqual(a, b) {
|
||||
return (a === b) ? "a and b are equal" : (a > b) ? "a is greater" : "b is greater";
|
||||
}
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -11,9 +11,26 @@ The <dfn>conditional operator</dfn>, also called the <dfn>ternary operator</dfn>
|
||||
The syntax is:
|
||||
<code>condition ? statement-if-true : statement-if-false;</code>
|
||||
The following function uses an if-else statement to check a condition:
|
||||
<blockquote>function findGreater(a, b) {<br> if(a > b) {<br> return "a is greater";<br> }<br> else {<br> return "b is greater";<br> }<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function findGreater(a, b) {
|
||||
if(a > b) {
|
||||
return "a is greater";
|
||||
}
|
||||
else {
|
||||
return "b is greater";
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
This can be re-written using the <code>conditional operator</code>:
|
||||
<blockquote>function findGreater(a, b) {<br> return a > b ? "a is greater" : "b is greater";<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function findGreater(a, b) {
|
||||
return a > b ? "a is greater" : "b is greater";
|
||||
}
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,25 @@ videoUrl: 'https://scrimba.com/c/cdBk8sM'
|
||||
<section id='description'>
|
||||
Objects can be thought of as a key/value storage, like a dictionary. If you have tabular data, you can use an object to "lookup" values rather than a <code>switch</code> statement or an <code>if/else</code> chain. This is most useful when you know that your input data is limited to a certain range.
|
||||
Here is an example of a simple reverse alphabet lookup:
|
||||
<blockquote>var alpha = {<br> 1:"Z",<br> 2:"Y",<br> 3:"X",<br> 4:"W",<br> ...<br> 24:"C",<br> 25:"B",<br> 26:"A"<br>};<br>alpha[2]; // "Y"<br>alpha[24]; // "C"<br><br>var value = 2;<br>alpha[value]; // "Y"</blockquote>
|
||||
|
||||
```js
|
||||
var alpha = {
|
||||
1:"Z",
|
||||
2:"Y",
|
||||
3:"X",
|
||||
4:"W",
|
||||
...
|
||||
24:"C",
|
||||
25:"B",
|
||||
26:"A"
|
||||
};
|
||||
alpha[2]; // "Y"
|
||||
alpha[24]; // "C"
|
||||
|
||||
var value = 2;
|
||||
alpha[value]; // "Y"
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -10,7 +10,11 @@ videoUrl: 'https://scrimba.com/c/cP3vVsm'
|
||||
We will now use our knowledge of strings to build a "<a href='https://en.wikipedia.org/wiki/Mad_Libs' target='_blank'>Mad Libs</a>" style word game we're calling "Word Blanks". You will create an (optionally humorous) "Fill in the Blanks" style sentence.
|
||||
In a "Mad Libs" game, you are provided sentences with some missing words, like nouns, verbs, adjectives and adverbs. You then fill in the missing pieces with words of your choice in a way that the completed sentence makes sense.
|
||||
Consider this sentence - "It was really <strong>____</strong>, and we <strong>____</strong> ourselves <strong>____</strong>". This sentence has three missing pieces- an adjective, a verb and an adverb, and we can add words of our choice to complete it. We can then assign the completed sentence to a variable as follows:
|
||||
<blockquote>var sentence = "It was really " + "hot" + ", and we " + "laughed" + " ourselves " + "silly" + ".";</blockquote>
|
||||
|
||||
```js
|
||||
var sentence = "It was really " + "hot" + ", and we " + "laughed" + " ourselves " + "silly" + ".";
|
||||
```
|
||||
|
||||
</section>
|
||||
|
||||
## Instructions
|
||||
|
||||
@@ -9,7 +9,13 @@ videoUrl: 'https://scrimba.com/c/cL6dqfy'
|
||||
<section id='description'>
|
||||
In JavaScript, we can divide up our code into reusable parts called <dfn>functions</dfn>.
|
||||
Here's an example of a function:
|
||||
<blockquote>function functionName() {<br> console.log("Hello World");<br>}</blockquote>
|
||||
|
||||
```js
|
||||
function functionName() {
|
||||
console.log("Hello World");
|
||||
}
|
||||
```
|
||||
|
||||
You can call or <dfn>invoke</dfn> this function by using its name followed by parentheses, like this:
|
||||
<code>functionName();</code>
|
||||
Each time the function is called it will print out the message <code>"Hello World"</code> on the dev console. All of the code between the curly braces will be executed every time the function is called.
|
||||
|
||||
Reference in New Issue
Block a user