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- <!DOCTYPE html>
- <html lang="en">
- <head>
- <meta charset="UTF-8">
- <meta name="viewport" content="width=device-width, initial-scale=1.0">
- <title>Document</title>
- </head>
- <body>
- <!--
- JS数据类型：
- 基本数据类型：
- Null Undefined Number Boolean String
- 引用数据类型
- Object Array Function
- -->
- <script>
- let obj = {
- name: 'Lucy',
- age: 10
- }
- let arr = [1,2,3,4,5,6];
- function fn1() {
- return "哈哈哈"
- }
- // 1.typeof
- // 能判断出： undefined string number boolean function
- // 不能判断出： null object array
- // console.log(typeof null); // object
- // console.log(typeof undefined); // undefined
- // console.log(typeof '1'); // string
- // console.log(typeof 3); // number
- // console.log(typeof true);// boolean
- // console.log(typeof obj); // object
- // console.log(typeof arr); // object
- // console.log(typeof fn1); // function
-
- // 2.obj(任意值) instanceof Object类型
- // console.log(obj instanceof Object); // true
- // console.log(arr instanceof Array); // true
- // console.log(fn1 instanceof Function); // true
- // 3.Object.prototype.toString.call()
- // console.log(Object.prototype.toString.call(1));// [Object Number]
- // console.log(Object.prototype.toString.call("21"));// [Object String]
- // console.log(Object.prototype.toString.call(true));// [Object Boolean]
- // console.log(Object.prototype.toString.call(undefined));// [Object Undefined]
- // console.log(Object.prototype.toString.call(null));// [Object Null]
- // console.log(Object.prototype.toString.call(fn1));// [Object Function]
- // console.log(Object.prototype.toString.call(arr));// [Object Array]
- // console.log(Object.prototype.toString.call(obj));// [Object Object]
- // 4.constructor
- // 不判断null和undefined
- console.log(false.constructor === Boolean); // true
- console.log((1).constructor === Number); // true
- console.log('2121'.constructor === String); // true
- console.log(obj.constructor === Object); //true
- console.log(arr.constructor === Array); //true
- console.log(fn1.constructor === Function); //true
- // console.log(null.constructor === null); //报错
- // console.log(undefined.constructor === undefined); // 报错
-
- </script>
- </body>
- </html>
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