Object.keys用法

Object.keys()方法会返回一个由一个给定对象的自身可枚举属性组成的数组。

var data={a:1,b:2,c:9,d:4,e:5};
	console.log(data);//{a: 1, b: 2, c: 9, d: 4, e: 5}
	console.log(Object.keys(data));//["a", "b", "c", "d", "e"]
	Object.keys(data).map((key,item)=>{
		console.log(key,data[key]);//key=>属性名    data[key]=>属性值
		});

Polyfill

要在原生不支持的旧环境中添加兼容的Object.keys，请复制以下代码段：

if (!Object.keys) {
  Object.keys = (function () { 
    var hasOwnProperty = Object.prototype.hasOwnProperty,
        hasDontEnumBug = !({toString: null}).propertyIsEnumerable('toString'),
        dontEnums = [
          'toString',
          'toLocaleString',
          'valueOf',
          'hasOwnProperty',
          'isPrototypeOf',
          'propertyIsEnumerable',
          'constructor'
        ],
        dontEnumsLength = dontEnums.length;

    return function (obj) {
      if (typeof obj !== 'object' && typeof obj !== 'function' || obj === null) throw new TypeError('Object.keys called on non-object');

      var result = [];

      for (var prop in obj) {
        if (hasOwnProperty.call(obj, prop)) result.push(prop);
      }

      if (hasDontEnumBug) {
        for (var i=0; i < dontEnumsLength; i++) {
          if (hasOwnProperty.call(obj, dontEnums[i])) result.push(dontEnums[i]);
        }
      }
      return result;
    }
  })()
};