156 lines
3.8 KiB
Markdown
156 lines
3.8 KiB
Markdown
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---
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id: a10d2431ad0c6a099a4b8b52
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title: Everything Be True
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challengeType: 5
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forumTopicId: 16011
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dashedName: everything-be-true
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---
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# --description--
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Check if the predicate (second argument) is <dfn>truthy</dfn> on all elements of a collection (first argument).
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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`.
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In JavaScript, `truthy` values are values that translate to `true` when evaluated in a Boolean context.
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Remember, you can access object properties through either dot notation or `[]` notation.
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# --hints--
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`truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex")` should return `true`.
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```js
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assert.strictEqual(
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truthCheck(
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[
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{ user: 'Tinky-Winky', sex: 'male' },
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{ user: 'Dipsy', sex: 'male' },
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{ user: 'Laa-Laa', sex: 'female' },
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{ user: 'Po', sex: 'female' }
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],
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'sex'
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),
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true
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);
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```
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`truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex")` should return `false`.
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```js
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assert.strictEqual(
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truthCheck(
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[
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{ user: 'Tinky-Winky', sex: 'male' },
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{ user: 'Dipsy' },
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{ user: 'Laa-Laa', sex: 'female' },
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{ user: 'Po', sex: 'female' }
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],
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'sex'
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),
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false
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);
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```
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`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")` should return `false`.
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```js
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assert.strictEqual(
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truthCheck(
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[
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{ user: 'Tinky-Winky', sex: 'male', age: 2 },
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{ user: 'Dipsy', sex: 'male', age: 0 },
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{ user: 'Laa-Laa', sex: 'female', age: 5 },
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{ user: 'Po', sex: 'female', age: 4 }
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],
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'age'
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),
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false
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);
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```
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`truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true}, {"name": "FastForward", "onBoat": null}], "onBoat")` should return `false`.
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```js
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assert.strictEqual(
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truthCheck(
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[
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{ name: 'Pete', onBoat: true },
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{ name: 'Repeat', onBoat: true },
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{ name: 'FastForward', onBoat: null }
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],
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'onBoat'
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),
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false
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);
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```
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`truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true, "alias": "Repete"}, {"name": "FastForward", "onBoat": true}], "onBoat")` should return `true`.
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```js
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assert.strictEqual(
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truthCheck(
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[
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{ name: 'Pete', onBoat: true },
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{ name: 'Repeat', onBoat: true, alias: 'Repete' },
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{ name: 'FastForward', onBoat: true }
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],
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'onBoat'
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),
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true
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);
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```
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`truthCheck([{"single": "yes"}], "single")` should return `true`.
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```js
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assert.strictEqual(truthCheck([{ single: 'yes' }], 'single'), true);
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```
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`truthCheck([{"single": ""}, {"single": "double"}], "single")` should return `false`.
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```js
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assert.strictEqual(
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truthCheck([{ single: '' }, { single: 'double' }], 'single'),
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false
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);
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```
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`truthCheck([{"single": "double"}, {"single": undefined}], "single")` should return `false`.
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```js
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assert.strictEqual(
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truthCheck([{ single: 'double' }, { single: undefined }], 'single'),
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false
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);
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```
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`truthCheck([{"single": "double"}, {"single": NaN}], "single")` should return `false`.
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```js
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assert.strictEqual(
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truthCheck([{ single: 'double' }, { single: NaN }], 'single'),
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false
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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 truthCheck(collection, pre) {
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return pre;
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}
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truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex");
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```
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# --solutions--
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```js
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function truthCheck(collection, pre) {
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return collection.every(function(e) { return e[pre]; });
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}
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```
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