详解Object.keys方法

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

1.传入对象，返回属性名

varobj = {'a':'123','b':'345'};

console.log(Object.keys(obj));//['a','b']

varobj1 = {100:"a",2:"b",7:"c"};

console.log(Object.keys(obj1));// console: ["2", "7", "100"]

varobj2 =Object.create({}, { getFoo : { value :function(){returnthis.foo } } });

obj2.foo =1;console.log(Object.keys(obj2));// console: ["foo"]

2.传入字符串，返回索引

varstr ='ab1234';

console.log(Object.keys(obj));//[0,1,2,3,4,5]

3.构造函数 返回空数组或者属性名

functionPasta(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: []

varspaghetti =newPasta("Tom",20,"male");    

console.log(Object.keys(spaghetti));//console: ["name", "age", "gender", "toString"]

4.数组 返回索引

vararr = ["a","b","c"];    

console.log(Object.keys(arr));// console: ["0", "1", "2"]