typeof

console.log(typeof a);    //undefined

console.log(typeof(true));  //boolean

console.log(typeof '111');  //string

console.log(typeof 111);   //number

console.log(typeof NaN);   //number

console.log(typeof null);  //object


var str = new String();

console.log(typeof(str));    //object

 
var  fn = function(){};

console.log(typeof(fn));  //function

 
class Box{

　　constructor（）{

　　}

}

var box = new Box（）；

console.log(typeof box);  //object

Object.prototype.toString.call();

console.log(Object.prototype.toString.call("aaa"));　　//[object String]
 
console.log(Object.prototype.toString.call(111));　　//[object Number]
 
console.log(Object.prototype.toString.call(true));　　//[object Boolean]
 
console.log(Object.prototype.toString.call(undefined));　　//[object Undefined]
 
console.log(Object.prototype.toString.call(null));　　//[object Null]
 
console.log(Object.prototype.toString.call({name: "zhang"}));　　//[object Object]
 
console.log(Object.prototype.toString.call(function(){}));　　//[object Function]
 
console.log(Object.prototype.toString.call([]));　　//[object Array]
 
console.log(Object.prototype.toString.call(new Date));　　//[object Date]
 
console.log(Object.prototype.toString.call(/a/));　　//[object RegExp]

class Test{
　　constructor(){

　　}
}
var test = new Test();
console.log(Object.prototype.toString.call(test));　　//[object Object]

constructor

console.log((111).constructor.name) 　　//Number

console.log(("111").constructor.name) 　　 //String

console.log((aaa).constructor.name)　　 //aaa is not defined

console.log((/a/).constructor.name)　　 //RegExp

console.log((true).constructor.name)　　 //Boolean

console.log(({name:"zhang"}).constructor.name)　　 //Object

console.log((new Date).constructor.name)　　 //Date

console.log(([]).constructor.name) 　　//Array

console.log((function(){}).constructor.name) 　　//Function

class Box{
　　constructor(){

　　}
}
var test = new Box();
console.log(test.constructor.name)　　 //Box