【判断JS数据类型】

  • JS 类型
1 null 
2 undefined
3 boolean
4 number
5 string　　
6 引用类型（object、array、function）
7 symbol

1.判断JS类型--typeof

判断 typeof(null) 时值为 'object'; 判断数组和对象时值均为 'object'

 1 const a = () => {
 2     return true
 3 } 5 typeof a
 6 "function"
 7 typeof 3
 8 "number"
 9 typeof '3'
10 "string"
11 typeof [3]
12 "object"
13 typeof {b: '3'}
14 "object"
15 typeof undefined
16 "undefined"
17 typeof null
18 "object"

2.判断JS类型 - Object.prototype.toString.call

对于所有基本的数据类型都能进行判断

 1 Object.prototype.toString.call(undefined)
 2 "[object Undefined]"
 3 Object.prototype.toString.call(null)
 4 "[object Null]"
 5 Object.prototype.toString.call(123)
 6 "[object Number]"
 7 Object.prototype.toString.call("123")
 8 "[object String]"
 9 Object.prototype.toString.call({})
10 "[object Object]"
11 Object.prototype.toString.call([])
12 "[object Array]"
13 Object.prototype.toString.call(a)
14 "[object Function]"
15 Object.prototype.toString.call(new Date())
16 "[object Date]"
17 Object.prototype.toString.call(Symbol())
18 "[object Symbol]"
19 Object.prototype.toString.call(Math)
20 "[object Math]"

3.判断JS类型 - instanceof 

这种方式只适合判断object类型

 

 1 const b = []
 2 b instanceof Array
 3 true
 4 b instanceof Object
 5 true
 6 b instanceof Function
 7 false
 8 --------------
 9 const c = {}
10 c instanceof Array
11 false
12 c instanceof Object
13 true
14 c instanceof Function
15 false
16 -------------
17 a instanceof Array
18 false
19 a instanceof Object
20 true
21 a instanceof Function
22 true

 

posted @ 2021-01-11 10:50  行屰  阅读(67)  评论(0)  编辑  收藏  举报