How to determine whether it is an object in javascript

Judgment method: 1. Use toString() to judge; 2. Use "obj.constructor === Object" to judge; 3. Use "ypeof obj === Object" to judge; 4. Use instanceof keyword to judge.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

1. toString() first choice

let obj = {} Object.prototype.toString.call(obj) === '[Object Object]'

2. constructor

let obj = {} obj.constructor === Object

【Recommended learning:js basic tutorial】

3. instanceof

Attention : Using instanceof to judge an array is also an object

let obj = {} obj instanceof Object //true let arr = [] arr instanceof Object //true

4, typeof

let obj = {} typeof obj === Object // 根据typeof判断对象也不太准确 表达式 返回值 typeof undefined 'undefined' typeof null 'object' typeof true 'boolean' typeof 123 'number' typeof "abc" 'string' typeof function() {} 'function' typeof {} 'object' typeof [] 'object'

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