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How to import javaScript files

王林

May 10, 2023 am 10:03 AM

With the development of web applications, JavaScript plays an increasingly important role in front-end development. When we start building a web application, we need to import JavaScript files to implement the front-end logic of the web application. In this article, we will discuss how to import JavaScript files and use them in web applications.

What is a JavaScript file?

A JavaScript file is a text file that contains JavaScript code for the front-end logic of a web application. JavaScript files usually have a .js file extension and contain JavaScript functions, variables, objects, etc.

Methods to import JavaScript files

JavaScript files can be imported into web applications through the following methods:

Quote directly in HTML files

The most common and simplest method is to reference JavaScript files in the head part or body part of the HTML file. You can use script tags to include JavaScript code or link to external JavaScript files. For example:

<!DOCTYPE html>
<html>
<head>
  <script src="path/to/your/javascript/file.js"></script>
</head>
<body>
  <!-- your HTML content here -->
</body>
</html>

In the above code, we use the <script></script> tag to introduce an external JavaScript file. The src attribute specifies the path to the JavaScript file. Paths can be relative or absolute. You can use relative paths if the file is in the same directory as the HTML file.

Using modular tools

Modern JavaScript applications often use modular tools to manage code. These tools allow splitting JavaScript code into multiple independent modules and loading them dynamically when needed. Importing JavaScript files using this method requires the use of corresponding modular tools, such as:

CommonJS: for Node.js applications.
AMD: used on the web browser side.
ES6 modules: for modern browsers and web applications.

The most commonly used of these tools is ES6 modules. ES6 modules are designed as a standard modular system that can import and export modules through ES6 module syntax (import and export). For example:

// file1.js
export const myFunction = () => {
  // function body
}

// file2.js
import { myFunction } from './file1.js';

In the above code, we export a function to file1.js and use the import statement in file2.js# Import this function in ##.

If your application uses the Node.js framework, you can use the require function to import JavaScript files. Using this approach requires support from a modular tool, such as CommonJS. For example:

// file1.js
module.exports = {
  myFunction: function() {
    // function body
  }
}

// file2.js
const file1 = require('./file1.js');
file1.myFunction();

In the above code, we export an object to

file1.js and use the require function in file2.js Import the object.

Summary

This article introduces several different methods of importing JavaScript files, including directly referencing them in HTML files, using modular tools, and using the require function in JavaScript files. No matter which method you choose, it will allow you to use JavaScript code in your web applications.

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