JS-Datentypen
Grundlegende Datentypen: String, Number, Null, Undefiniert, [Boolean]
Referenzdatentypen: Object, Array, Function
So zeigen Sie Datentypen in JavaScript an
- Wenn Sie typeof zum Anzeigen von Datentypen verwenden, sind Null und Arrays Objekttypen.
- Die Methode Object.prototype.toString.call() ist die detaillierteste.
- Die Methode von „constructor.name“ kann null und undefiniert nicht prüfen.
1. Variablentyp
console.log(typeof 1);//number
console.log(typeof "HELLO WORLD");//string
console.log(typeof null);//object
console.log(typeof undefined);//undefined
console.log(typeof true);//Boolean
console.log(typeof false);//Boolean
console.log(typeof {
name:"xiaoming"});//object
console.log(typeof function(){
});//function
Zwei, Object.prototype.toString.call (Variable)
console.log(Object.prototype.toString.call(1));//[object Number]
console.log(Object.prototype.toString.call("HELLO WORLD"));//[object String]
console.log(Object.prototype.toString.call(null));//[object Null]
console.log(Object.prototype.toString.call(undefined));//[object Undefined]
console.log(Object.prototype.toString.call(true));//[object Boolean]
console.log(Object.prototype.toString.call(false));//[object Boolean]
console.log(Object.prototype.toString.call({
name:"xiaoming"}));[object Object]
console.log(Object.prototype.toString.call(function(){
}));//[object Function]
console.log(Object.prototype.toString.call([1,2,3,"a"]));//[object Array]
Drei, variabler Konstruktor
let a=1;
let b="HELLO WORLD";
let c=null;
let d=undefined;
let e=true;
let f=false;
let g={
name:"xiaoming"};
let h=function(){
};
let i=[1,2,3,"a"];
console.log(a.constructor.name);//Number
console.log(b.constructor.name);//String
//console.log(c.constructor.name);//报错:'constructor' of null
//console.log(d.constructor.name);//报错:'constructor' of undefined
console.log(e.constructor.name);//Boolean
console.log(f.constructor.name);//Boolean
console.log(g.constructor.name);//Object
console.log(h.constructor.name);//Function
console.log(i.constructor.name);//Array