TypeScript判断对象类型的四种方式
一、typeof
typeof ""; //string
typeof 1; //number
typeof false; //boolean
typeof undefined; //undefined
typeof function(){}; //function
typeof {}; //object
typeof Symbol(); //symbol
typeof null; //object
typeof []; //object
typeof new Date(); //object
typeof new RegExp(); //object
二、instanceof
{} instanceof Object; //true
[] instanceof Array; //true
[] instanceof Object; //true
"123" instanceof String; //falsenew String(123) instanceof String; //true
三、constructor
function instance(left,right){
let prototype = right.prototype; //获取类型的原型
let proto = left.__proto__; //获取对象的原型
while(true){ //循环判断对象的原型是否等于类型的原型,直到对象原型为null,因为原型链最终为null
if (proto === null || proto === undefined){
return false;
}
if (proto === prototype){
return true;
}
proto = proto.__proto__;
}
}
console.log(instance({},Object)); //true
console.log(instance([],Number)); //false
四、Object.prototype.toString()
function getType(obj){
let type = typeof obj;
if(type != "object"){
return type;
}
return Object.prototype.toString.call(obj).replace(/^\[object (\S+)\]$/, '$1');
}
使用案例:
百度一下,你就知道