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92 lines
2.5 KiB
Markdown
92 lines
2.5 KiB
Markdown
---
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id: 587d7b8a367417b2b2512b4c
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title: >-
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Destructuring via rest elements
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challengeType: 1
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forumTopicId: 301218
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dashedName: >-
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use-destructuring-assignment-with-the-rest-parameter-to-reassign-array-elements
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---
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# --description--
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In manchen Situationen, in denen es um die Destrukturierung von Arrays geht, möchten wir vielleicht die restlichen Elemente in einem separaten Array sammeln.
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Das Ergebnis ist ähnlich wie bei `Array.prototype.slice()`, wie unten gezeigt:
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```js
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const [a, b, ...arr] = [1, 2, 3, 4, 5, 7];
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console.log(a, b);
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console.log(arr);
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```
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Die Konsole würde die Werte `1, 2` und `[3, 4, 5, 7]` anzeigen.
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Die Variablen `a` und `b` entnehmen den ersten und zweiten Wert aus dem Array. After that, because of the rest syntax presence, `arr` gets the rest of the values in the form of an array. Das Rest-Element funktioniert nur als letzte Variable in der Liste richtig. As in, you cannot use the rest syntax to catch a subarray that leaves out the last element of the original array.
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# --instructions--
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Use a destructuring assignment with the rest syntax to emulate the behavior of `Array.prototype.slice()`. `removeFirstTwo()` should return a sub-array of the original array `list` with the first two elements omitted.
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# --hints--
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`removeFirstTwo([1, 2, 3, 4, 5])` should be `[3, 4, 5]`
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```js
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const testArr_ = [1, 2, 3, 4, 5];
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const testArrWORemoved_ = removeFirstTwo(testArr_);
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assert(testArrWORemoved_.every((e, i) => e === i + 3) && testArrWORemoved_.length === 3);
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```
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`removeFirstTwo()` should not modify `list`
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```js
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const testArr_ = [1, 2, 3, 4, 5];
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const testArrWORemoved_ = removeFirstTwo(testArr_);
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assert(testArr_.every((e, i) => e === i + 1) && testArr_.length === 5);
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```
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`Array.slice()` sollte nicht verwendet werden.
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```js
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(getUserInput) => assert(!getUserInput('index').match(/slice/g));
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```
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Die Destrukturierung auf `list` sollte verwendet werden.
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```js
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assert(
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__helpers
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.removeWhiteSpace(code)
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.match(/\[(([_$a-z]\w*)?,){1,}\.\.\.shorterList\]=list/i)
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);
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```
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# --seed--
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## --seed-contents--
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```js
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function removeFirstTwo(list) {
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// Only change code below this line
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const shorterList = list; // Change this line
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// Only change code above this line
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return shorterList;
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}
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const source = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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const sourceWithoutFirstTwo = removeFirstTwo(source);
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```
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# --solutions--
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```js
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function removeFirstTwo(list) {
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const [, , ...shorterList] = list;
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return shorterList;
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}
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const source = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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const sourceWithoutFirstTwo = removeFirstTwo(source);
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```
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