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How to understand the objects in JavaScript, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain for you in detail, people with this need can come to learn, I hope you can gain something.

A brief introduction to objects in JavaScript

We know that everything that exists objectively in life is an object, so what is the object in the program like? We can understand the object in the program as a representation of the object in the client world in a computer. Objects mentioned in all programming languages are similar in nature, and they often correspond to an area in memory where object property or method information is stored.

The creation of objects in JavaScript

Create objects based on {} symbols

In JS, we can define objects directly based on {}, and define properties and methods in the object content, for example:

In JS, we can think of an object as a structure that encapsulates properties and methods, such as

If you need to create multiple objects with the same structure over and over again, using {} code is redundant-repetitive. It's not easy to maintain!

Create an object based on a constructor

If we want to easily define multiple objects with the same structure but different attribute values in JS, we can create objects directly based on the constructor (a special function that defines the same attribute structure of multiple objects of the same type), for example:

Suggestion: as long as you repeatedly create multiple objects with the same structure, use constructors to create objects.

In practical applications, we try not to define functions in constructors, such as:

In this way, when building objects, you may need to open up additional function space every time.

Object properties in JavaScript

Package characteristic

Objects in JS are used to encapsulate properties and methods. As shown in the figure:

Inherit property

In order to realize the reusability of properties or methods in JS, an inheritance mechanism is provided.

This kind of inheritance needs to be realized with the help of Prototype object, which is automatically created when the constructor is defined, and is used to store all common properties and methods. All objects constructed by this constructor inherit this prototype object.

The prototype object analysis in the constructor, as shown in the figure:

Inheritance of prototype object (ProtoType) objects, as shown in the figure:

Add common attributes to the object, as shown in the figure:

To add a common method to the object. As shown in the figure:

Multiple common methods are added simultaneously based on the JS prototype object, as shown in the figure:

Prototype chain is a chain structure formed by the inheritance of multi-level parent objects (prototype objects) step by step. This prototype chain holds all the parent prototype objects that an object can access, as well as all the properties and methods that can be accessed by that object.

Polymorphic characteristics

Polymorphism generally refers to the same function (behavior), showing different states in different situations. From the application, there are two forms, namely overloading and rewriting.

Definition of overloading: a function that performs different logic depending on the values of the arguments passed in.

Overridden definition: defines a member in the child object with the same name as the member in the parent object. As long as what you inherit from the parent object doesn't work, rewrite your own!

Define a self-owned member in the child object with the same name as the member in the parent object, for example:

JavaScript built-in object type

Introduction to object Typ

The type of object in JavaScript can be understood as the combination of constructor and prototype object. When we need to check its object type, we can use the constructor name.

Object types built into JS

There are 11 built-in object types in JS, namely String, Number, Boolean, Array, Date, RegExp, Math (object), Error, Function, Object, global (object)

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