JavaScript 判断数据类型的三种常用方法详解

    typeof 1 // "number"
    typeof "a" // "string"
    typeof true // "boolean"
    typeof {} // "object"
    typeof [] // "object"
    typeof function(){} // "function"

Object.prototype.toString.call(2);//"[object Number]"
Object.prototype.toString.call("s");//"[object String]"
Object.prototype.toString.call(true);//"[object Boolean]"

Object.prototype.toString.call(null);//"[object Null]"
Object.prototype.toString.call(undefined);//"[object Undefined]"

Object.prototype.toString.call({});//"[object Object]"
Object.prototype.toString.call([]);//"[object Array]"
Object.prototype.toString.call(function(){});//"[object Function]"
Object.prototype.toString.call(String);//"[object Function]"
var t = new Date();
Object.prototype.toString.call(t);//"[object Date]"
var bb = new Boolean();
Object.prototype.toString.call(bb);//"[object Boolean]"
var bb = new Number();
Object.prototype.toString.call(bb);//"[object Number]"
var str = new String();
Object.prototype.toString.call(str);//"[object String]"
var reg = new RegExp("^1[34578][0-9]{9}$","g");
Object.prototype.toString.call(reg);//"[object RegExp]"
var reg = Math.valueOf();
Object.prototype.toString.call(reg);//"[object Math]"

var isNativeJSON = window.JSON && Object.prototype.toString.call(JSON);
console.log(isNativeJSON);//[object JSON]

function Foo(name,age) {
this.name = name;
this.age = age;
}
var foo =new Foo("harry",20);
Object.prototype.toString.call(foo);//"[object Object]"

console.log(foo instanceof Foo);//true