The 4 stages of object creation using the new keyword

Question Analysis

Look at the code first

var Func=function(){
};
var func=new Func ();

new has gone through 4 stages in total

1. Create an empty object

var obj=new Object();

2. Set the prototype chain

obj.__proto__= Func.prototype;

3, let this in Func point to obj, and execute the function body of Func.

var result =Func.call(obj);

4. Determine the return value type of Func:

If it is a value type, return obj. If it is a reference type, an object of this reference type is returned.

if (typeof(result) == "object"){  func=result;}else{    func=obj;;}

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