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