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"]
