Thoroughly master prototype__ proto__、 Relationship before constructor (JS prototype, prototype chain)

One 、 First map

Two 、prototype、proto、constructor The rules

Rule one ： Instance does not prototype, Example of constructor Pointing constructor , Example of __proto__ Point to the prototype of the upper layer ( That is, the constructor prototype).

Rule 2 ：Object、 Constructors 、Function All are Function Example .

example ： Combine these two rules , In the picture f1 yes Foo Example ,Foo、Object、Function Are all Function Example . The direction is very clear .

Rule three ： The prototype of the function __proto__ Point to the prototype of the upper layer （ That is to say Fun.prototype.proto Point to Object.prototype）

Rule 4 ： The prototype of the function constructor Point to the function itself （ It can be understood as prototype and constructor Offset ）

example ： Combine the three four rules , The figure below also goes through .

3、 ... and 、 Code up

function Fun(){
    

}

const f1 = new Fun()

console.log(f1.constructor === Fun)
console.log(f1.__proto__ === Fun.prototype)
console.log(Function.prototype === Function.__proto__)
console.log(Fun.prototype.constructor === Fun)
console.log(Fun.prototype.__proto__ === Function.__proto__.__proto__)
console.log(Fun.constructor.__proto__ === Function.prototype)
console.log(Object.constructor === Function)
console.log(Function.constructor === Function)
console.log(Function.prototype.__proto__ === Object.prototype)
console.log(Object.prototype.__proto__ === null)

// The results are all true

summary ： When the relationship in the picture has been printed in my mind , Try to write the transformation equation between the three by yourself , And various nesting .
for example ：new Fun().constructor.proto.proto === Object.prototype