Can I use classes in JavaScript?-Front-end Q&A-php.cn

Can I use classes in JavaScript?

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Release： 2022-10-20 14:03:41

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Class can be used in JavaScript; a class is a function, but instead of using the keyword function for initialization, use the keyword class and assign attributes in the constructor() method, each time the class object is initialized , the constructor() method will be called, and the syntax is "class className{constructor(){...}}".

Can I use classes in JavaScript?

The operating environment of this tutorial: Windows 10 system, JavaScript version 1.8.5, Dell G3 computer.

Class can be used in JavaScript

A class is a function, but instead of using the keyword function to initialize it, you use the keyword class and assign properties in the constructor() method.

Every time a class object is initialized, the constructor() method is called.

Note: Unlike function and other JavaScript declarations, class declarations are not hoisted (you must declare a class before you can use it).

Note: The syntax in the class must be written in "strict mode".

The syntax is:

class className {
  // 类主体
}

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We use the class keyword to create a class. The class body is in a pair of braces {}. We can define the location of the class members in the braces {}. , such as a method or constructor.

Each class contains a special method constructor(), which is the constructor of the class. This method is used to create and initialize an object created by class.

The example is as follows:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>123</title>
</head>
<body>
<h2>JavaScript 类</h2>
<p>如何使用 JavaScript 类</p>
<p id="demo"></p>
<script>
class Runoob {
  constructor(name, url) {
    this.name = name;
    this.url = url;
  }
}
 
let site = new Runoob("好好学习",  "//m.sbmmt.com");
document.getElementById("demo").innerHTML =
site.name + "：" + site.url;
</script>
</body>
</html>

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Output result:

Can I use classes in JavaScript?

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