194 lines
2.7 KiB
Markdown
194 lines
2.7 KiB
Markdown
---
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title: ES6
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layout: default
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---
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## Stable (io.js)
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New features you can use on io.js.
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### Promises
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```js
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new Promise(fn)
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.then(fn)
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.catch(fn)
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Promise.all(/*...*/)
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Promise.race(/*...*/)
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Promise.reject(/*...*/)
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Promise.resolve(/*...*/)
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```
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### Block scoping
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```js
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// Block scoping (let)
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function fn () {
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let x = 0;
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if (true) {
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let x = 1; // only inside this `if`
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}
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}
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// Constants
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const a = 1;
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```
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### Backtick strings
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```js
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// interpolation
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var message = `Hello ${name}`;
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// Multiline
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var str = `
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hello
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world
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`;
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```
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### Syntax improvements
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```js
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// Short object syntax
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// aka: `exports = { hello:hello, bye:bye }`
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module.exports = { hello, bye };
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// New string methods
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"hello".repeat(3)
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"hello".contains("ll")
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"\u1E9B\u0323".normalize("NFC")
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// Binary/octal literals
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var bin = 0b1010010;
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var oct = 0755;
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```
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## Stable ([Babel])
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Available via [Babel]
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### Module imports
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```js
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// Import; aka: require('...')
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import 'helpers';
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// Import; aka: Express = require('...')
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import Express from 'express';
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// Import; aka: indent = require('...').indent
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import { indent } from 'helpers';
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```
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### Module exports
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```js
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// Export; aka: module.exports = ...
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export default function () {
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// ...
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};
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// Export a method; aka: exports.mymethod = ...
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export function mymethod () {
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};
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// Export a value; aka: exports.pi = ...
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export var pi = 3.14159;
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```
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### Destructuring
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```js
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// Destructuring assignment
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var [first, last] = ["Nikola", "Tesla"];
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let {title, author} = { title: "The Silkworm", author: "R. Galbraith" };
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// Available in loops too
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for (let {title, artist} in songs) {
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// ...
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}
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// Functions
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function greet({ name, greeting }) {
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// ...
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}
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greet({ name: "Larry", greeting: "Ahoy" });
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```
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### Function arguments
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```js
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// Default arguments
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function greet(name="Jerry") {
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return `Hello ${name}`;
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}
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// Spread arguments
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function fn(x, ...y) {
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// y is an Array
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return x * y.length;
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}
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// Rest
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fn(...[1,2,3]) // same as fn(1,2,3)
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```
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### Fat arrows
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```js
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// Fat arrows
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setTimeout(() => {
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console.log('hi');
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});
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// Short syntax (no `return` without `{}`)
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numbers.map(n => n * 2)
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```
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### Classes
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```js
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class Circle extends Shape {
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// ctor
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constructor(radius) {
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this.radius = radius;
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}
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// methods
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getArea() {
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return Math.PI * 2 * this.radius;
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}
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// calling super methods
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expand(n) {
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return super.expand(n) * Math.PI;
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}
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// static methods
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static createFromDiameter(diameter) {
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return new Circle(diameter / 2);
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}
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}
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```
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## Experimental
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Available via 6to5's experimental mode
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```js
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/*
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* Comprehensions
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*/
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// Basic comprehension
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var names = [for (c of customers) c.name];
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// Comprehension with IDs
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var names = [for (c of customers) if (c.admin) c.name];
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```
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[Babel]: http://babeljs.io
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