判断内置对象

代码

let obj = {
    id: 1001,
    name : 'test'
};

let arr = [
  'hello',
  'world',
];

let date = new Date();

利用对象的构造函数的 name 属性来判断对象类型

console.log(obj.constructor.name); // Object
console.log(arr.constructor.name); // Array
console.log(date.constructor.name); // Date

借调 Object 的 toString 方法

console.log(Object.prototype.toString.call(date)); // [object Date]
console.log(Object.prototype.toString.call(obj));  // [object Object]
console.log(Object.prototype.toString.call(arr));  // [object Array]
console.log(Object.prototype.toString.call("1")); // [object String]
console.log(Object.prototype.toString.call(10)); // [object Number]
console.log(Object.prototype.toString.call(true)); // [object Boolean]

判断自定义对象

代码

function Dog(name) {
    this.name = name;
}

function Cat(name) {
    this.name = name;
}

function Person(name) {
    this.name = name;
}
let p = new Person("person");
let c = new Cat("cat");
let d = new Dog("dog");

利用对象的构造函数的 name 属性来判断对象类型

console.log(p.constructor.name); // Person
console.log(c.constructor.name); // Cat
console.log(d.constructor.name); // Dog

利用 instanceof 运算符

console.log(p instanceof Person); // true
console.log(c instanceof Person); // false
console.log(d instanceof Person); // false

console.log(p instanceof Object); // true
console.log(d instanceof Object); // true
console.log(c instanceof Object); // true