91 lines
2.4 KiB
Markdown
91 lines
2.4 KiB
Markdown
---
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id: 587d7b87367417b2b2512b43
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title: Use Arrow Functions to Write Concise Anonymous Functions
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challengeType: 1
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---
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## Description
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<section id='description'>
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In JavaScript, we often don't need to name our functions, especially when passing a function as an argument to another function. Instead, we create inline functions. We don't need to name these functions because we do not reuse them anywhere else.
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To achieve this, we often use the following syntax:
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```js
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const myFunc = function() {
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const myVar = "value";
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return myVar;
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}
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```
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ES6 provides us with the syntactic sugar to not have to write anonymous functions this way. Instead, you can use <strong>arrow function syntax</strong>:
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```js
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const myFunc = () => {
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const myVar = "value";
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return myVar;
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}
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```
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When there is no function body, and only a return value, arrow function syntax allows you to omit the keyword <code>return</code> as well as the brackets surrounding the code. This helps simplify smaller functions into one-line statements:
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```js
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const myFunc = () => "value"
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```
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This code will still return <code>value</code> by default.
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</section>
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## Instructions
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<section id='instructions'>
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Rewrite the function assigned to the variable <code>magic</code> which returns a new <code>Date()</code> to use arrow function syntax. Also make sure nothing is defined using the keyword <code>var</code>.
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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 should replace <code>var</code> keyword.
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testString: getUserInput => assert(!getUserInput('index').match(/var/g));
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- text: <code>magic</code> should be a constant variable (by using <code>const</code>).
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testString: getUserInput => assert(getUserInput('index').match(/const\s+magic/g));
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- text: <code>magic</code> should be a <code>function</code>.
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testString: assert(typeof magic === 'function');
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- text: <code>magic()</code> should return correct date.
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testString: assert(magic().setHours(0,0,0,0) === new Date().setHours(0,0,0,0));
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- text: <code>function</code> keyword should not be 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 magic = function() {
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"use strict";
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return new Date();
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};
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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 magic = () => {
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"use strict";
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return new Date();
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};
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```
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</section>
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