Object.keys方法详解

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在实际开发中，我们有时需要知道对象的所有属性，原生js给我们提供了一个很好的方法：Object.keys()，该方法返回一个数组

传入对象，返回属性名

var obj = {'a':'123','b':'345'};console.log(Object.keys(obj));  //['a','b']var obj1 = { 100: "a", 2: "b", 7: "c"};console.log(Object.keys(obj1)); // console: ["2", "7", "100"]var obj2 = Object.create({}, { getFoo : { value : function () { return this.foo } } });obj2.foo = 1;console.log(Object.keys(obj2)); // console: ["foo"]

传入字符串，返回索引

var str = 'ab1234';console.log(Object.keys(obj));  //[0,1,2,3,4,5]

构造函数返回空数组或者属性名

    function Pasta(name, age, gender) {            this.name = name;            this.age = age;            this.gender = gender;            this.toString = function () {                    return (this.name + ", " + this.age + ", " + this.gender);            }    }    console.log(Object.keys(Pasta)); //console: []    var spaghetti = new Pasta("Tom", 20, "male");    console.log(Object.keys(spaghetti)); //console: ["name", "age", "gender", "toString"]

数组返回索引

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

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