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Definition method of javascript script

PHPzOriginal: 2023-05-21 10:24:081077browse

JavaScript is a scripting language widely used in website development, user interface design, mobile application development and other fields. In this rapidly changing digital age, JavaScript is an essential programming tool. So, how to define JavaScript script? In this article, we will discuss how to define JavaScript scripts.

1. What is JavaScript script?

JavaScript script is a lightweight programming language that is based on the ECMAScript standard and combines features of other languages, such as C language and Java language. It is widely used in web development, game development, desktop application development and other fields.

JavaScript scripts can run on both the client side (browser) and the server side (Node.js). It can work together with HTML, CSS and other languages to achieve the effect of dynamic web pages.

2. Define JavaScript scripts in HTML documents

There are two ways to define JavaScript scripts in HTML documents.

Use the 3f1c4e4b6b16bbbd69b2ee476dc4f83a tag to define JavaScript scripts

The3f1c4e4b6b16bbbd69b2ee476dc4f83a tag is used to define JavaScript scripts and is placed in the 93f0f5c25f18dab9d176bd4f6de5d30e or b3c3442f9f778cf47f676b3dcab32550 in the middle of the tag. The following is an example of using the 3f1c4e4b6b16bbbd69b2ee476dc4f83a tag:

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript脚本</title>
  <script>
    function showMessage() {
      alert('Hello, JavaScript!');
    }
  </script>
</head>
<body onload="showMessage()">
  <h1>JavaScript脚本示例</h1>
</body>
</html>

In the above code, the 3f1c4e4b6b16bbbd69b2ee476dc4f83a tag defines a showMessage() function, which uses the alert() method to display in the pop-up box a message. An onload event is defined in the 6c04bd5ca3fcae76e30b72ad730ca86d tag. When the page is loaded, the showMessage() function will be executed.

Place JavaScript code in elements defined in HTML documents

In addition to using the 3f1c4e4b6b16bbbd69b2ee476dc4f83a tag to define JavaScript scripts, you can also place JavaScript code in HTML documents In elements defined in , such as bb9345e55eb71822850ff156dfde57c8, , etc. The following is an example of using the tag to define a JavaScript script:

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript脚本</title>
</head>
<body>
  <a href="javascript:alert('Hello, JavaScript!')">点击我</a>
</body>
</html>

In the above code, the tag defines an onclick event. When the element is clicked, a message box will pop up.

3. Defining JavaScript scripts in external JavaScript files

There is a disadvantage of defining JavaScript scripts in HTML documents, that is, when the amount of script code is large, it will increase the size of the HTML document, affecting Page loading speed. To solve this problem, you can define the JavaScript code in an external file and then reference the file in the HTML document.

The following is an example of an external JavaScript file named script.js, which contains a showMessage() function:

function showMessage() {
  alert('Hello, JavaScript!');
}

The way to reference the script.js file in an HTML document is as follows :

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript脚本</title>
  <script src="script.js"></script>
</head>
<body onload="showMessage()">
  <h1>JavaScript脚本示例</h1>
</body>
</html>

In the above code, the src attribute of the 3f1c4e4b6b16bbbd69b2ee476dc4f83a tag points to the path to the external JavaScript file. When the HTML document is loaded, the file is automatically loaded and the code in it is executed.

Summary

This article introduces three methods of defining JavaScript scripts: defining in an HTML document, placing JavaScript code in an element defined in an HTML document, and defining in an external JavaScript file . Each method has its own advantages and disadvantages, and the most appropriate method is chosen based on the specific situation. As a web developer, it is very important to have an in-depth understanding of JavaScript, which helps improve development efficiency and code quality.

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