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Detailed explanation of the difference between constructors with parentheses and without parentheses

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Release: 2018-01-02 15:47:41
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This article mainly brings you a detailed discussion of the difference between constructors with parentheses and without parentheses. The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor to take a look, I hope it can help everyone.

As shown below:

//首先定义一个构造函数Hello

function Hello(){
  alert(1);
}

//定义一个函数表达式

var getName = function(){
  alert(2);
}

//实例化对象,下面这两个如果构造函数没有形参的话,实例化的时候构造函数可以不加括号(推荐加上);

var p = new Hello;
var p1 = new Hello();

//但是用下边的方式调用getName函数的时候,构造函数有没有括号可就不一样了;

new Hello.getName(); //这种执行顺序是先执行Hello.getName(),然后在使用new关键字;
new Hello().getName;//这种是先new Hello()一个对象,然后对象调用getName方法;
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