Object.keys方法之详解

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”]

转载自：https://www.geek-share.com/detail/2689878447.html