Object.keys() . Object.assign()

1.来不及了，直接看代码吧

补充一点：
Object.keys 只收集自身属性名，不收集继承自原型链上的
Object.keys（obj），返回一个数组，数组里是该obj可被枚举的所有属性，以数组的形式返回。请看示例：

示例1

    function Pasta(grain, width, shape) {
            this.grain = grain;
            this.width = width;
            this.shape = shape;
            this.toString = function () {
                    return (this.grain + ", " + this.width + ", " + this.shape);
            }
    }

    console.log(Object.keys(Pasta)); //console: []
    var spaghetti = new Pasta("wheat", 0.2, "circle");
    console.log(Object.keys(spaghetti)); //console: ["grain", "width", "shape", "toString"]

console.log(Object.keys(Pasta)); //console: []
//解释，由于没有将构造函数实例化，所以只打印了一个空数组
实例化之后，就将构造函数所有的属性都作为一个数组进行返回

实例二

    var arr = ["a", "b", "c"];
    console.log(Object.keys(arr)); // console: ["0", "1", "2"]

    var obj = { 0 : "a", 1 : "b", 2 : "c"};
    console.log(Object.keys(obj)); // console: ["0", "1", "2"]


    var an_obj = { 100: "a", 2: "b", 7: "c"};
    console.log(Object.keys(an_obj)); // console: ["2", "7", "100"]


    var my_obj = Object.create({}, { getFoo : { value : function () { return this.foo } } });
    my_obj.foo = 1;

    console.log(Object.keys(my_obj)); // console: ["foo"]

当传入的是数组时候，返回的是数组的下标
是传入对象，则返回对应的属性

Object.assign

自己实现一个

if(typeof Object.assign != function){
  Object.defineProperty(Object, 'assign', {
    value: function(target, varArgs){
      if(type target != null){
        let to = Object(target);
        for(var i=0; i< arguments.length; i++ ){
          nextSource = arguments[index]
          if(nextSource != null){
             for (let nextKey in nextSource) {
            // Avoid bugs when hasOwnProperty is shadowed
            if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
              to[nextKey] = nextSource[nextKey];
            }
           }
          }
        }
       return to
      }
    },
    writeable: true,
    configurable: true
  })
}