2b265e3404
* Add example of arrow function with no brackets Add an example of the shorter option of an arrow function * Fixed typo
71 lines
1.8 KiB
Markdown
71 lines
1.8 KiB
Markdown
---
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title: Arrow Functions
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---
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## Arrow functions
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ES6 has introduced a new syntax that allows to declare functions.
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```javascript
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// Old Syntax
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function oldOne() {
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console.log("Hello World..!");
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}
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// New Syntax
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const newOne = () => {
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console.log("Hello World..!");
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}
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// Or on one line
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const newOne = () => console.log("Hello World..!");
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```
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The new syntax may be confusing. There are two major parts of it.
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1. const newOne = ()
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2. => {}
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The first part is just declaring a variable and assigning the function (i.e) () to it. It just says the variable is actually a function. The `const` keyword is used to indicate that the function won't be reassigned. Refer [this](https://github.com/freeCodeCamp/freeCodeCamp/blob/master/guide/english/javascript/es6/let-and-const/index.md) to learn more about `const` and `let`.
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Then the second part is declaring the body part of the function. The arrow part with the curly braces defines the body part.
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Another example with parameters:
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```javascript
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let NewOneWithParameters = (a, b) => {
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console.log(a+b); // 30
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}
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NewOneWithParameters(10, 20);
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```
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Parentheses are optional when there's only one parameter name:
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```javascript
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let newOneWithOneParam = a => {
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console.log(a);
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}
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```
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When there is only one statement or operation in the function body, braces are optional and the result is returned or undefined.
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```javascript
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let a = 10;
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let newOneParamWithNoBrackets = b => a + b;
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console.log(newOneParamWithNoBrackets(20)); // 30
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```
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An incredible advantage of the arrows function is that you can not rebind an arrow function. It will always be called with the context in which it was defined. Just use a normal function.
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```javascript
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// Old Syntax
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axios.get(url).then(function(response) {
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this.data = response.data;
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}).bind(this);
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// New Syntax
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axios.get(url).then(response => {
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this.data = response.data;
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});
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```
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