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what is javascript tag

王林

Release： 2023-05-16 09:51:07

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The

JavaScript tag is a special tag used to embed JavaScript code in HTML documents. It allows developers to write JavaScript code to change the content of HTML documents, add animation effects, respond to user actions, and more. In Web development, JavaScript is widely used, from the development of front-end interactive properties to the writing of back-end server Node.js applications, it has become one of the important components of Web development.

Among them, the most common application scenario of JavaScript tags is to introduce external JavaScript files into HTML documents. Developers can use the <script> tag in an HTML document to introduce a URL to a JavaScript file into the document. For example:

<html>
  <head>
    <title>My Page</title>
    <script src="my_script.js"></script>
  </head>
  <body>
    ...
  </body>
</html>

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In this example, the HTML document references a JavaScript file named my_script.js through the <script> tag. When the browser parses this tag, it will automatically download and execute the specified JavaScript file.

In addition, you can also write JavaScript code directly in the <script> tag, for example:

<html>
  <head>
    <title>My Page</title>
    <script>
      alert("Hello, JavaScript!");
    </script>
  </head>
  <body>
    ...
  </body>
</html>

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In this example, <script># Write a piece of JavaScript code directly into the ## tag. When the browser parses the tag, it will automatically execute the code and pop up a warning box containing "Hello, JavaScript!"

In addition to the above usage, the

<script type="text/javascript">
  // JavaScript code here
</script>

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In In HTML5, the default value of the

type attribute is "text/javascript" and can be omitted. In addition, the <script> tag also has a defer attribute, which can delay script execution until the document is parsed, which can effectively improve page loading speed:

<script type="text/javascript" defer>
  // JavaScript code here
</script>

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In short, JavaScript tag is one of the very important tags in web development, and developers need to be proficient in using it to write efficient web applications.

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