js之精确的区分数据类型

1. typeof

主要用于判断数据是不是基本数据类型：string、number、object、undefined、boolean，但是无法判断出function（有些浏览器会出错）、array、regExp、null

console.log(typeof '');//string  
console.log(typeof []);//object  
console.log(typeof {});//object  
console.log(typeof 1);//number  
console.log(typeof null);//object  
console.log(typeof undefined);//undefined  
console.log(typeof true);//boolean  
console.log(typeof function(){});//function  
console.log(typeof /d/);//object  

2. instanceof

主要的目的是用来检测引用类型，判断Array和RegExp，无法准确判断Function

console.log([] instanceof Array);//true  
console.log({} instanceof Object);//true  
console.log(/d/ instanceof RegExp);//true  
console.log(function(){} instanceof Object);//true  
console.log(function(){} instanceof Function);//true  

console.log('' instanceof String);//false  
console.log(1 instanceof Number);//false

3. Object.prototype.toString

对象的一个原生原型扩展函数，用来精确的区分数据类型

Object.prototype.toString.call(data).slice(8,-1) === 'Array'

var type=Object.prototype.toString;  
console.log(type.call(''));//[object String]
console.log(type.call([]));//[object Array]  
console.log(type.call({}));//[object Object]  
console.log(type.call(false));//[object Boolean]  
console.log(type.call(null));//[object Null]  
console.log(type.call(undefined));//[object Undefined]  
console.log(type.call(function(){}));//[object Function]