What are the definition methods of javascript classes

The methods are: 1. Constructor method, syntax "function Cat(){}var cat1=new Cat();}"; 2. Object.create() method, syntax "var Cat={}" ;var cat1=Object.create(Cat);”.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

In object-oriented programming, a class is a template for an object, which defines the properties and methods common to the same group of objects (also called "instances").

The Javascript language does not support "classes", but you can use some workarounds to simulate "classes".

1. Constructor method

This is a classic method and a method that must be taught in textbooks. It uses a constructor to simulate a "class" and uses the this keyword internally to refer to the instance object.

　　function Cat() { 　　　　this.name = "大毛"; 　　}

When generating an instance, use the new keyword.

　　var cat1 = new Cat(); 　　alert(cat1.name); // 大毛

The attributes and methods of the class can also be defined on the prototype object of the constructor.

　　Cat.prototype.makeSound = function(){ 　　　　alert("喵喵喵"); 　　}

For a detailed introduction to this method, please read the series of articles I wrote "Javascript Object-Oriented Programming", so I won’t go into details here. Its main disadvantage is that it is relatively complicated, uses this and prototype, and is very laborious to write and read.

2. Object.create() method

In order to solve the shortcomings of the "constructor method" and generate objects more conveniently, the fifth edition of ECMAScript, the international standard for Javascript (The current version is the third version), which proposes a new method Object.create().

Using this method, "class" is an object, not a function.

　　var Cat = { 　　　　name: "大毛", 　　　　makeSound: function(){ alert("喵喵喵"); } 　　};

Then, use Object.create() to generate an instance directly, without using new.

　　var cat1 = Object.create(Cat); 　　alert(cat1.name); // 大毛 　　cat1.makeSound(); // 喵喵喵

Currently, the latest versions of all major browsers (including IE9) have deployed this method. If you encounter an old browser, you can use the following code to deploy it yourself.

　　if (!Object.create) { 　　　　Object.create = function (o) { 　　　　　　 function F() {} 　　　　　　F.prototype = o; 　　　　　　return new F(); 　　　　}; 　　}

This method is simpler than the "constructor method", but it cannot implement private properties and private methods, nor can it share data between instance objects, and the simulation of "classes" is not comprehensive enough.

[Recommended learning:javascript advanced tutorial]

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