javascript:得到变量类型的方法(chrome 105.0.5195.125)

一，js代码:

<html>
<head>
    <meta charset="utf-8"/>
    <title>测试</title>
</head>
<body>
<script>
//一，用typeof 得到变量的类型

let one = 'a';
console.log(typeof one);

one = 1;
console.log(typeof one);

one = true;
console.log(typeof one);

one = Symbol();
console.log(typeof one);

one = undefined;
console.log(typeof one);

one = new Function();
console.log(typeof one);

//二，用toString.call得到变量的类型

one = 'a';
console.log(typeof one);
console.log(toString.call(one));
one = 1;
console.log(typeof one);
console.log(toString.call(one));
one = true;
console.log(typeof one);
console.log(toString.call(one));
one = Symbol();
console.log(typeof one);
console.log(toString.call(one));
one = undefined;
console.log(typeof one);
console.log(toString.call(one));
one = new Function();
console.log(typeof one);
console.log(toString.call(one));
//说明：可以看到 对象,null,数组,Date,Error等被typeof统一识别成 object
//     这种情况下使用toString.call更准确
one = null;
console.log(typeof one);
console.log(toString.call(one));
one = {};
console.log(typeof one);
console.log(toString.call(one));
one = [1,2,3];
console.log(typeof one);
console.log(toString.call(one));
one = new RegExp();
console.log(typeof one);
console.log(toString.call(one));
one = new Date();
console.log(typeof one);
console.log(toString.call(one));
one = new Error();
console.log(typeof one);
console.log(toString.call(one));
one = window;
console.log(typeof one);
console.log(toString.call(one));
one = document;
console.log(typeof one);
console.log(toString.call(one));

//三，用instanceof判断是否某个类的实例:

function A(name,age){
  this.name = name;
  this.age = age;
}

let a = new A('张三',18);
console.log(a instanceof A);

class myClass{
    constructor(name,age){
        this.name=name
        this.age=age
    }
}
let i=new myClass('小明',18);
console.log(i instanceof myClass);
console.log(i instanceof A);
console.log(typeof i);
console.log(toString.call(i));

//四，constructor方法，因为不支持undefined和null,不再举例

</script>
</body>
</html>

说明：刘宏缔的架构森林是一个专注架构的博客，

网站：https://blog.imgtouch.com
本文: https://blog.imgtouch.com/index.php/2023/06/03/javascript-de-dao-bian-liang-lei-xing-de-fang-fa-chrome-105/

         对应的源码可以访问这里获取： https://github.com/liuhongdi/
         或: https://gitee.com/liuhongdi

说明：作者:刘宏缔 邮箱: 371125307@qq.com

二，测试效果

三，查看chrome的版本:

 

posted @ 2022-10-06 21:31  刘宏缔的架构森林  阅读(88)  评论(0)    收藏  举报