freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/everything-be-true.english.md

id, title, isRequired, challengeType, forumTopicId

id	title	isRequired	challengeType	forumTopicId
a10d2431ad0c6a099a4b8b52	Everything Be True	true	5	16011

Description

Check if the predicate (second argument) is truthy on all elements of a collection (first argument). In other words, you are given an array collection of objects. The predicate pre will be an object property and you need to return true if its value is truthy. Otherwise, return false. In JavaScript, truthy values are values that translate to true when evaluated in a Boolean context. Remember, you can access object properties through either dot notation or [] notation.

Instructions

Tests

tests:
  - text: '<code>truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex")</code> should return true.'
    testString: 'assert.strictEqual(truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex"), true);'
  - text: '<code>truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex")</code> should return false.'
    testString: 'assert.strictEqual(truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex"), false);'
  - text: '<code>truthCheck([{"user": "Tinky-Winky", "sex": "male", "age": 0}, {"user": "Dipsy", "sex": "male", "age": 3}, {"user": "Laa-Laa", "sex": "female", "age": 5}, {"user": "Po", "sex": "female", "age": 4}], "age")</code> should return false.'
    testString: 'assert.strictEqual(truthCheck([{"user": "Tinky-Winky", "sex": "male", "age": 2}, {"user": "Dipsy", "sex": "male", "age": 0}, {"user": "Laa-Laa", "sex": "female", "age": 5}, {"user": "Po", "sex": "female", "age": 4}], "age"), false);'
  - text: '<code>truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true}, {"name": "FastForward", "onBoat": null}], "onBoat")</code> should return false'
    testString: 'assert.strictEqual(truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true}, {"name": "FastForward", "onBoat": null}], "onBoat"), false);'
  - text: '<code>truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true, "alias": "Repete"}, {"name": "FastForward", "onBoat": true}], "onBoat")</code> should return true'
    testString: 'assert.strictEqual(truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true, "alias": "Repete"}, {"name": "FastForward", "onBoat": true}], "onBoat"), true);'
  - text: '<code>truthCheck([{"single": "yes"}], "single")</code> should return true'
    testString: 'assert.strictEqual(truthCheck([{"single": "yes"}], "single"), true);'
  - text: '<code>truthCheck([{"single": ""}, {"single": "double"}], "single")</code> should return false'
    testString: 'assert.strictEqual(truthCheck([{"single": ""}, {"single": "double"}], "single"), false);'
  - text: '<code>truthCheck([{"single": "double"}, {"single": undefined}], "single")</code> should return false'
    testString: 'assert.strictEqual(truthCheck([{"single": "double"}, {"single": undefined}], "single"), false);'
  - text: '<code>truthCheck([{"single": "double"}, {"single": NaN}], "single")</code> should return false'
    testString: 'assert.strictEqual(truthCheck([{"single": "double"}, {"single": NaN}], "single"), false);'

Challenge Seed

function truthCheck(collection, pre) {
  return pre;
}

truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex");

Solution

function truthCheck(collection, pre) {
  return collection.every(function(e) { return e[pre]; });
}