ES5 和 ES6 对象遍历方法

1. for...in
2. for...of
3. Object.keys()
4. Object.getOwnPropertyNames()
5. Reflect.ownKeys()
6. Object.getOwnPropertyDescriptors()

for...in

遍历可枚举的自由属性或继承的属性，不包括 Symbol 属性

var obj = {
  name: "hello",
  career: "world",
  [Symbol()]: "symbolValue"
};
Object.defineProperty(obj, "age", {
  value: "23",
  enumerable: false
});
Object.prototype.protoPer1 = function() {
  console.log("proto");
};
Object.prototype.protoPer2 = 2;
for (var key in obj) {
  console.log(`key:${key}`);
}
// 输出
// key:name
// key:career
// key:protoPer1
// key:protoPer2

for...of

只能遍历可枚举的自由属性，不能遍历 Symbol 和继承属性

var obj = {
  name: "hello",
  career: "world",
  [Symbol()]: "symbolValue"
};
Object.defineProperty(obj, "age", {
  value: "23",
  enumerable: false
});
Object.prototype.protoPer1 = function() {
  console.log("proto");
};
Object.prototype.protoPer2 = 2;
// 如何用for of遍历对象
let { keys, values, entries } = Object;
for (let [key, value] of entries(obj)) {
  console.log(key, value);
}
// 输出
// name hello
// career world

Object.keys()

以数组形式返回对象的自有可枚举属性，不包括 Symbol 属性

var obj = {
  name: "hello",
  career: "world",
  [Symbol()]: "symbolValue"
};
Object.defineProperty(obj, "age", {
  value: "23",
  enumerable: false
});
Object.prototype.protoPer1 = function() {
  console.log("proto");
};
Object.prototype.protoPer2 = 2;
console.log(Object.keys(obj));
Object.keys(obj);
// 输出
// ["name", "career"]

Object.getOwnPropertyNames()

以数组形式返回对象的自有可枚举或不可枚举属性，不包括 Symbol 属性

var obj = {
  name: "hello",
  career: "world",
  [Symbol()]: "symbolValue"
};
Object.defineProperty(obj, "age", {
  value: "23",
  enumerable: false
});
Object.prototype.protoPer1 = function() {
  console.log("proto");
};
Object.prototype.protoPer2 = 2;
console.log(Object.getOwnPropertyNames(obj));
// 输出
// ["name", "career", "age"]

Reflect.ownKeys()

以数组形式返回对象的自有可枚举或不可枚举属性，包含 Symbol 属性

var obj = {
  name: "hello",
  career: "world",
  [Symbol()]: "symbolValue"
};
Object.defineProperty(obj, "age", {
  value: "23",
  enumerable: false
});
Object.prototype.protoPer1 = function() {
  console.log("proto");
};
Object.prototype.protoPer2 = 2;
console.log(Reflect.ownKeys(obj));
// 输出
// ["name", "career", "age", Symbol()]

Object.getOwnPropertyDescriptors()

返回对象的自有属性描述符，包含 Symbol 属性描述符

var obj = {
  name: "hello",
  career: "world",
  [Symbol()]: "symbolValue"
};
Object.defineProperty(obj, "age", {
  value: "23",
  enumerable: false
});
Object.prototype.protoPer1 = function() {
  console.log("proto");
};
Object.prototype.protoPer2 = 2;
console.log(Object.getOwnPropertyDescriptors(obj));
// 输出
// {age: {value: "23", writable: false, enumerable: false, configurable: false},
// career: {value: "world", writable: true, enumerable: true, configurable: true},
// name: {value: "hello", writable: true, enumerable: true, configurable: true},
// Symbol(): {value: "symbolValue", writable: true, enumerable: true, configurable: true}}