Prototype and prototype chain in JS

1） Prototype

2） Prototype chain ： Find the properties and methods of the object
1、 The object itself cannot find
2、 Constructor find
3、 Object prototype find
4、 Constructor prototype find
5、 Look up in the prototype ------》 Keep looking up , Until I can't find it | So far to find
At the top of the prototype chain is null, The object cannot be found. The attribute is undefined

		function Fun(){
    
            this.test1=function(){
    
                console.log('test1');
            }
        }
        Fun.prototype.test2=function(){
    
            console.log('test2');
        }
        var fun=new Fun()
        fun.test1()// Own attributes 
        fun.test2()// Found on the prototype chain 
        console.log(fun.toString());// Constructors Fun Prototype object , It's also object An instantiated object of ,
        // Follow this prototype chain to find Object Upper toString Method 

3）JS Modification and rewriting of prototype in
modify

        function Person(name){
    
            this.name=name
        }
        Person.prototype.getName=function(){
    
            console.log(ths.name);
        }
        var p=new Person(' Zhang San ')
        console.log(p.__proto__===Person.prototype);//true
        console.log(p.constructor);//ƒ Person(name){this.name = name}
        console.log(p.__proto__===p.constructor.prototype);//true

rewrite

Direct to Person The prototype object of is assigned with an object ,p The constructor of points to the root constructor object

        function Person(name){
    
            this.name=name
        }
        // Rewriting prototype 
        Person.prototype={
    
            getName:function(){
    
                console.log(this.name);
            }
        }
        var p=new Person(' Zhang San ')
        console.log(p.__proto__===Person.prototype);//true
        console.log(p.__proto__);//{getName:f}
        console.log(p.constructor.prototype);//{costructor:...}
        console.log(p.__proto__===p.constructor.prototype);//false
        p.constructor=Person
        console.log(p.__proto__ === p.constructor.prototype);//true

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