ES6

Ref:https://github.com/lukehoban/es6features

arrows箭头

和 C# 的lambda表达式没什么区别。

classes类

ES6 classes are a simple sugar over the prototype-based OO pattern.

Classes support prototype-based inheritance, super calls, instance and static methods and constructors.

类支持基于原型的继承，super调用，实例和静态方法和构造函数。

class SkinnedMesh extends THREE.Mesh {
  constructor(geometry, materials) {
    super(geometry, materials);

    this.idMatrix = SkinnedMesh.defaultMatrix();
    this.bones = [];
    this.boneMatrices = [];
    //...
  }
  update(camera) {
    //...
    super.update();
  }
  get boneCount() {
    return this.bones.length;
  }
  set matrixType(matrixType) {
    this.idMatrix = SkinnedMesh[matrixType]();
  }
  static defaultMatrix() {
    return new THREE.Matrix4();
  }
}

enhanced object literals

template strings字符串模板

var name = "Bob", time = "today";
`Hello ${name}, how are you ${time}?`

destructuring解构

自动解析数组或对象中的值.

var [x,y]=getVal(),//函数返回值的解构
    [name,,age]=['wayou','male','secrect'];//数组解构

function getVal() {
    return [ 1, 2 ];
}

console.log('x:'+x+', y:'+y);//输出：x:1, y:2 
console.log('name:'+name+', age:'+age);//输出： name:wayou, age:secrect

default + rest + spread默认+不定+延展

这三个均为参数的特性：

默认参数

function f(x, y=12) {
// y is 12 if not passed (or passed as undefined)
return x + y;
}
f(3) == 15

不定参数

function f(x, ...y) {
// y is an Array
return x * y.length;
}
f(3, "hello", true) == 6

延展参数

function f(x, y, z) {
return x + y + z;
}
// Pass each elem of array as argument
f(...[1,2,3]) == 6

let + const

let 局部的var

const静态

iterators + for..of

generators

unicode

modules模块

// lib/math.js
export function sum(x, y) {
  return x + y;
}
export var pi = 3.141593;

// app.js
import * as math from "lib/math";
alert("2π = " + math.sum(math.pi, math.pi));

// otherApp.js
import {sum, pi} from "lib/math";
alert("2π = " + sum(pi, pi));

module loaders

map + set + weakmap + weakset

// Sets
var s = new Set();
s.add("hello").add("goodbye").add("hello");
s.size === 2;
s.has("hello") === true;

// Maps
var m = new Map();
m.set("hello", 42);
m.set(s, 34);
m.get(s) == 34;

// Weak Maps
var wm = new WeakMap();
wm.set(s, { extra: 42 });
wm.size === undefined

// Weak Sets
var ws = new WeakSet();
ws.add({ data: 42 });
// Because the added object has no other references, it will not be held in the set

proxies代理

// Proxying a normal object
var target = {};
var handler = {
  get: function (receiver, name) {
    return `Hello, ${name}!`;
  }
};

var p = new Proxy(target, handler);
p.world === 'Hello, world!';

// Proxying a function object
var target = function () { return 'I am the target'; };
var handler = {
  apply: function (receiver, ...args) {
    return 'I am the proxy';
  }
};

var p = new Proxy(target, handler);
p() === 'I am the proxy';

更多的运行时元操作：

var handler =
{
  get:...,
  set:...,
  has:...,
  deleteProperty:...,
  apply:...,
  construct:...,
  getOwnPropertyDescriptor:...,
  defineProperty:...,
  getPrototypeOf:...,
  setPrototypeOf:...,
  enumerate:...,
  ownKeys:...,
  preventExtensions:...,
  isExtensible:...
}

另一个例子：

var engineer = { name: 'Joe Sixpack', salary: 50 };

var interceptor = {
  set: function (receiver, property, value) {
    console.log(property, 'is changed to', value);
    receiver[property] = value;
  }
};

engineer = Proxy(engineer, interceptor);
engineer.salary = 60;//salary is changed to 60

symbols符号

var MyClass = (function() {

  // module scoped symbol
  var key = Symbol("key");

  function MyClass(privateData) {
    this[key] = privateData;
  }

  MyClass.prototype = {
    doStuff: function() {
      ... this[key] ...
    }
  };

  return MyClass;
})();

var c = new MyClass("hello")
c["key"] === undefined

subclassable built-ins

promises

//创建promise
var promise = new Promise(function(resolve, reject) {
    // 进行一些异步或耗时操作
    if ( /*如果成功 */ ) {
        resolve("Stuff worked!");
    } else {
        reject(Error("It broke"));
    }
});
//绑定处理程序
promise.then(function(result) {
    //promise成功的话会执行这里
    console.log(result); // "Stuff worked!"
}, function(err) {
    //promise失败会执行这里
    console.log(err); // Error: "It broke"
});

ES6

ES6