ECMAScript 6 新内容一览

1. let, const (定义块级局部变量), 函数在块级域中

2. 解构: let {x, y} = pt; let [s, v, o] = triple(); (如可以 let pt = {x:2, y:-5}).

3. 参数设置默认设置: function f(x, y=1, z=0) {...}

4. rest: function g(i, j, ...r) { return r.slice(i, j); } (而不是疯狂地使用arguments).

5. spread: let a = [0,1,2,3], o = new Something(...a);

6. proxies: let obj = Proxy.create(handler, proto). 简单地说，就是类对象元素的符号重载.

7. weak map: let map = new WeakMap. 当你有循环应用的时候用它.

8. generators: function* gen() { yield 1; yield 2; } 事实上, gen() 返回一个有next()属性的对象

9. 迭代器: for (var [key, val] of items(x)) { alert(key + ',' + val); }. Iterators 可以是 generators 或者 proxies.

10. array and generator comprehension: [a+b for (a in A) for (b in B)] (array comprehension), (x for (x of generateValues()) if (x.color === 'blue')) (generator expression).

11. 二进制数据: const Pixel = new StructType({x:uint32, y:uint32, color:Color}) (此处Color本身就是一个结构类型), new ArrayType(Pixel, 3).

12. 类语法, 包含 extends, prototype, and super:

    class Point extends Base {
      constructor(x,y) {
        super();
        this[px] = x, this[py] = y;
        this.r = function() { return Math.sqrt(x*x + y*y); }
      }
      get x() { return this[px]; }
      get y() { return this[py]; }
      proto_r() { return Math.sqrt(this[px] * this[px] +
          this[py] * this[py]); }
      equals(p) { return this[px] === p[px] &&
          this[py] === p[py]; }
    }

13.  模块:

    module math {
      export function sum(x, y) {
        return x + y;
      }
      export var pi = 3.141593;
    }
    import {sum, pi} from math;
    alert(sum(pi,pi));

14. quasis: multiline, 可扩展的预处理字符串. You are ${age} years old.

    // The following regexp spans multiple lines.
    re`line1: (words )*
    line2: \w+`
    
    // It desugars to:
    re({raw:'line1: (words )*\nline2: \w+',
        cooked:'line1: (words )*\nline2: \w+'}) 

作者：Barret Lee 出处：hustskyking.cnblogs.com