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This article is to share with you about what the js prototype chain is, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

The prototype chain is a mechanism that means that every object in the JavaScript, including the prototype object, has a built-in [[proto]] property that points to the prototype object of the function object that created it, the prototype property.

Function: the existence of prototype chain is mainly to realize the inheritance of objects.

Several concepts about the prototype chain:

1. Function object

In JavaScript, a function is an object.

2. Prototype object

When you define a function object, it contains a predefined property called prototype, which is called the prototype object.

/ / function object function F () {}; console.log (F.prototype)

3 、 _ _ proto__

When JavaScript creates an object, it always has a built-in property of [[proto]] that points to the prototype of the function object that created it. The prototype object also has a [[proto]] property. Therefore, in the constant pointing, the prototype chain is formed.

For example, if we modify the prototype object of object F, we can clearly see the above relationship.

/ / function object function F () {}; F.prototype = {hello: function () {}}; var f = new F (); console.log (f.

4 、 new

When you use new to call the constructor, it is equivalent to executing the

Var o = {}; o.protoprotoplast _ = F.prototypetic F.Call (o)

Therefore, new plays a key role in the implementation of the prototype chain.

5 、 constructor

The prototype object prototype has a predefined constructor property that refers to its function object. This is a circular reference.

Function F () {}; F.prototype.constructor = = F

In practical application, there are often the following ways to write

Function F () {}; F.prototype = {constructor: F, doSomething: function () {}}

The reason for adding constructor here is that if the prototype object is rewritten, the constructor property disappears and needs to be manually fixed.

6. Memory structure of prototype chain

Function F () {this.name = 'zhang';}; var F1 = new F (); var f2 = new F (); this is what the js prototype chain is, and the editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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