ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
92 lines
2.1 KiB
Markdown
92 lines
2.1 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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forumTopicId: 301211
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dashedName: use-arrow-functions-to-write-concise-anonymous-functions
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---
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# --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 **arrow function syntax**:
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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 `return` 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 the string `value` by default.
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# --instructions--
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Rewrite the function assigned to the variable `magic` which returns a `new Date()` to use arrow function syntax. Also, make sure nothing is defined using the keyword `var`.
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# --hints--
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User should replace `var` keyword.
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```js
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(getUserInput) => assert(!getUserInput('index').match(/var/g));
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```
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`magic` should be a constant variable (by using `const`).
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```js
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(getUserInput) => assert(getUserInput('index').match(/const\s+magic/g));
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```
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`magic` should be a `function`.
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```js
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assert(typeof magic === 'function');
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```
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`magic()` should return correct date.
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```js
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assert(magic().setHours(0, 0, 0, 0) === new Date().setHours(0, 0, 0, 0));
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```
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`function` keyword should not be used.
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```js
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(getUserInput) => assert(!getUserInput('index').match(/function/g));
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```
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# --seed--
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## --seed-contents--
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```js
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var magic = function() {
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return new Date();
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};
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```
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# --solutions--
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```js
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const magic = () => {
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return new Date();
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};
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```
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