几种判断数据类型的优缺点
一、typeof
console.log(typeof 1); // number console.log(typeof true); // boolean console.log(typeof 'mc'); // string console.log(typeof function(){}); // function console.log(typeof []); // object console.log(typeof {}); // object console.log(typeof null); // object console.log(typeof undefined); // undefined 优点:能够快速区分基本数据类型 缺点:不能将Object、Array和Null区分,都返回object
二、instanceof
console.log(1 instanceof Number); // false console.log(true instanceof Boolean); // false console.log('str' instanceof String); // false console.log([] instanceof Array); // true console.log(function(){} instanceof Function); // true console.log({} instanceof Object); // true 优点:能够区分Array、Object和Function,适合用于判断自定义的类实例对象 缺点:Number,Boolean,String基本数据类型不能判断
三、Object.prototype.toString.call()
var toString = Object.prototype.toString; console.log(toString.call(1)); //[object Number] console.log(toString.call(true)); //[object Boolean] console.log(toString.call('mc')); //[object String] console.log(toString.call([])); //[object Array] console.log(toString.call({})); //[object Object] console.log(toString.call(function(){})); //[object Function] console.log(toString.call(undefined)); //[object Undefined] console.log(toString.call(null)); //[object Null] 优点:精准判断数据类型 缺点:写法繁琐不容易记,推荐进行封装后使用