91 lines
2.1 KiB
Markdown
91 lines
2.1 KiB
Markdown
---
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id: 587d7b88367417b2b2512b44
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title: Write Arrow Functions with Parameters
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challengeType: 1
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forumTopicId: 301223
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---
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## Description
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<section id='description'>
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Just like a regular function, you can pass arguments into an arrow function.
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```js
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// doubles input value and returns it
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const doubler = (item) => item * 2;
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```
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If an arrow function has a single argument, the parentheses enclosing the argument may be omitted.
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```js
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// the same function, without the argument parentheses
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const doubler = item => item * 2;
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```
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It is possible to pass more than one argument into an arrow function.
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```js
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// multiplies the first input value by the second and returns it
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const multiplier = (item, multi) => item * multi;
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```
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</section>
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## Instructions
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<section id='instructions'>
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Rewrite the <code>myConcat</code> function which appends contents of <code>arr2</code> to <code>arr1</code> so that the function uses arrow function syntax.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: User did replace <code>var</code> keyword.
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testString: getUserInput => assert(!getUserInput('index').match(/var/g));
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- text: <code>myConcat</code> should be a constant variable (by using <code>const</code>).
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testString: getUserInput => assert(getUserInput('index').match(/const\s+myConcat/g));
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- text: <code>myConcat</code> should be a function
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testString: assert(typeof myConcat === 'function');
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- text: <code>myConcat()</code> returns the correct <code>array</code>
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testString: assert(() => { const a = myConcat([1], [2]); return a[0] == 1 && a[1] == 2; });
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- text: <code>function</code> keyword was not used.
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testString: getUserInput => assert(!getUserInput('index').match(/function/g));
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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var myConcat = function(arr1, arr2) {
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"use strict";
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return arr1.concat(arr2);
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};
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// test your code
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console.log(myConcat([1, 2], [3, 4, 5]));
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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const myConcat = (arr1, arr2) => {
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"use strict";
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return arr1.concat(arr2);
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};
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// test your code
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console.log(myConcat([1, 2], [3, 4, 5]));
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```
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</section>
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