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This article mainly introduces what the javascript prototype means. It is very detailed and has a certain reference value. Friends who are interested must finish it!

All JavaScript objects have a built-in Prototype private property that points to another object, which we call the prototype of the original object.

This article operating environment: windows7 system, javascript1.8.5 version, Dell G3 computer.

Learning objectives:

Know what js is prototype, prototype, constituent function, instance object relationship; prototype application scope.

What is a prototype?

The function has a prototype, and the function has a property called prototype. The prototype of the function points to an object, which is called the prototype object. The prototype object has a constructor property that points to the function itself.

There is also a prototype of the instance object, and the prototype object is generally called the _ _ proto__,__proto__ stealth prototype. This stealth prototype has a constructor attribute that points to the constructor that created the instance.

Direct relationship between constructor, instance object, and prototype

Relationship between constructor and instance object

There is also a constructor property in the _ _ proto__ in each instance object, which points to the constructor that created the instance:

The relationship between instance object _ _ proto__ and constructor prototype

In each instance object, the _ _ proto__ points to the constructor where the two prototype are equal.

Constructor, prototype prototype object, instance object, proto,constructor, direct relationship

Prototype function

One of the prototype functions: data sharing, saving memory space

The second part of the prototype function: in order to realize inheritance

How to share data and save memory space in prototype

JavaScript object-oriented programming

How does the prototype realize inheritance

For example, there is now a constructor for an "animal" object.

There is also a constructor for the cat object.

How can we make the cat inherit the animal?

If the cat's prototype object points to an instance of Animal, then all instances of the cat can inherit Animal.

The diagram of the relationship between cat1 instance object and constructor is as follows

Any prototype object has a constructor property that points to its constructor.

Add Cat.prototype = new Animal (); after the code

Cat.prototype.constructor points to Animal.

The diagram of the relationship between cat1 instance object and constructor is as follows

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