myVar.constructor - 或 - typeof myVar ---有什么区别？ [英] myVar.constructor --or-- typeof myVar ---What is the difference?

问题描述

有什么区别......

What is the difference between...

if(myVar.constructor == String)

和

if(typeof myVar == "string")

推荐答案

表达式 myVar.constructor 只返回成员constructor的值。对于给定对象来说，拥有一个指向字符串（或其他任何东西）的构造函数是完全可能和合法的。例如

The expression myVar.constructor just returns the value of the member "constructor". It's completely possible and legal for a given object to have a constructor which points to string (or anything else). For example

function Apple() {}
var x = new Apple();
x.constructor = String
if (x.constructor == String) {
  // True
}

使用 typeof 运算符提供您正在寻找的信息

Using the typeof operator though provides the information you're looking for

if (typeof myVar == 'string') {
  // It's a string
}

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