typeof：
用于判断number/string/boolean/underfined类型/function
不能判断：null和object ，不能区分object和Array
instanceof：
判断具体的对象类型
===：
用于判断undefined和null
//五种基本类型
var num=1;
var str="abc";
var bl=true;
var nu=null;
var undef=undefined;
//三种特殊类型
var obj=new Object();
var arr2=["1",2,true];
var fun=function () {
}
write("-------typeof-----------")
write(num,typeof num);//1 number
write(str,typeof str);//abc string
write(bl,typeof bl);//true boolean
write(nu,typeof nu);//null object
write(undef,typeof undef)//undefined undefined
write(obj,typeof obj);//[object Object] object
write(arr2,typeof arr2);//1,2,true object
write("-----------===-----------")
write(num,typeof num==="number");//1 true
write(str,typeof str==="string");//abc true
write(bl,typeof bl==="boolean");//true true
write(nu,typeof nu==="object");//null true
write(undef,typeof undef==="undefined")//undefined true
write(obj,typeof obj==="object");//[object Object] true
write(arr2,typeof arr2==="object");//1,2,true true
write(fun,typeof fun==="function");//function () { } true
write("---------instanceof---------------")
write(obj,obj instanceof Object)//[object Object] true
write(arr2,arr2 instanceof Array);//1,2,true true
write(arr2,arr2 instanceof Object);//1,2,true true
write(fun, fun instanceof Function)//function () { } true
write(fun, fun instanceof Object)//function () { } true