實際開發(fā)中，有時候需要知道對象的所有屬性，原生js提供了一個很好的方法：
Object.keys()，該方法返回一個數(shù)組
傳入對象，返回屬性名
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"]
傳入字符串，返回索引
var str = 'ab1234';
console.log(Object.keys(obj)); //[0,1,2,3,4,5]
構(gòu)造函數(shù) 返回空數(shù)組或者屬性名
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"]
數(shù)組 返回索引
var arr = ["a", "b", "c"];
console.log(Object.keys(arr)); // console: ["0", "1", "2"]
