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📜  pre html - Javascript (1)

📅  最后修改于: 2023-12-03 15:03:51.781000             🧑  作者: Mango

Pre-HTML with JavaScript

Introduction

Pre-HTML with JavaScript is a technique that allows you to manipulate the DOM before the HTML has been fully loaded by the browser. This can be useful in a variety of situations, such as when you want to perform some operations on the DOM, or if you want to inject external scripts into the page.

In this article, we will explore how to use Pre-HTML with JavaScript and provide some examples of its usefulness.

How It Works

Pre-HTML works by using JavaScript to manipulate the DOM directly. This means that you can insert, modify, or remove HTML elements before the DOM is fully loaded. You can also inject external scripts into the page using the document.write() function.

To use Pre-HTML, you need to place your JavaScript code in the <head> section of your HTML file. This ensures that the JavaScript code is executed before the body content is loaded.

Here is an example:

<head>
  <script>
    // Pre-HTML with JavaScript example
    document.getElementById("myDiv").innerHTML = "Hello, world!";
  </script>
</head>
<body>
  <div id="myDiv"></div>
</body>

In this example, the JavaScript code sets the innerHTML property of a <div> element with an id of "myDiv" to "Hello, world!" before the <div> element has been loaded.

Use Cases
Injecting External Scripts

One common use case for Pre-HTML is to inject external scripts into the page. This is often done when you need to load a script from a remote URL or when you want to conditionally load a script based on some criteria.

Here is an example:

<head>
  <script>
    // Pre-HTML with JavaScript example
    if (someCondition) {
      document.write('<script src="https://example.com/external-script.js"><\/script>');
    }
  </script>
</head>
<body>
  <!-- Body content -->
</body>

In this example, the JavaScript code checks some condition and, if it is true, it injects an external script into the page using the document.write() function.

Modifying the DOM

Another use case for Pre-HTML is to modify the DOM directly. This can be useful if you want to perform some operations on the DOM before it is fully loaded.

Here is an example:

<head>
  <script>
    // Pre-HTML with JavaScript example
    document.getElementById("myDiv").innerHTML = "Hello, world!";
  </script>
</head>
<body>
  <div id="myDiv"></div>
</body>

In this example, the JavaScript code modifies the innerHTML property of a <div> element with an id of "myDiv" before the <div> element has been loaded.

Conclusion

Pre-HTML with JavaScript is a powerful technique that allows you to manipulate the DOM before the HTML has been fully loaded by the browser. It can be useful in a variety of situations, such as when you want to perform some operations on the DOM or if you want to inject external scripts into the page.

By placing your JavaScript code in the <head> section of your HTML file, you can ensure that it is executed before the body content is loaded. This allows you to take full advantage of Pre-HTML with JavaScript to create dynamic and interactive web pages.