JS prototype and prototype chain (Lantern Festival meal)

Today is the Lantern Festival , I wish you all a happy Lantern Festival ！ Today, let's talk about prototype and prototype chain ~

First of all, we make it clear that the prototype exists in the constructed functions , Arrays and classes have no prototype ~

So let's start with the constructor , Then add some attributes to the function prototype to test .

 function person(){
           this.say=function(){
               console.log(" In the constructor ");
           }
       }

In the existing function person Prototype under prototype Add attribute to test .

 person.prototype.say=function(){
           console.log(" Functions in the prototype ");
       } 

When all the above is done, we will start Create examples And directly create a name attribute ：

var p1 = new person();

p1.name=" Li Si ";

Then create on the prototype name And age attribute ：

 person.prototype.name=" Zhang San ";

 person.prototype.age = 18;

After all the above steps are completed , We can start testing ！

Background printing ,say The method calls in the constructor ;age Is in the prototype ;name It's an example of .

It can be explained in this way , The background is to find the current instance attribute first , If you find it , Then print it out , If it is not found, it will follow the prototype chain layer by layer , Finally, if the value found in the prototype chain is null Print out in the background undefined.