How does webpack import from external url

When working with Webpack for frontend projects, we commonly handle resources and modules within the project, including JavaScript and CSS files. However, sometimes you may need to import resources from external URLs, which is not part of Webpack's default behavior. Nevertheless, there are several methods to achieve importing resources from external URLs.

Method One: Externals Configuration

Webpack allows you to specify certain modules as external in the configuration, meaning these modules are fetched from external sources at runtime rather than being bundled into the output file. This is particularly useful when dealing with CDN resources or other external libraries.

For example, if you want to load jQuery from a CDN instead of bundling it into your bundle, you can configure it in webpack.config.js as follows:

javascript
module.exports = {
  // Other configurations...
  externals: {
    jquery: 'jQuery'
  }
}

Then, in your code, you can still reference jQuery normally:

javascript
import $ from 'jquery';

$('body').text('Hello, world!');

At runtime, Webpack expects a jQuery variable to be available in the global scope, which should be loaded via CDN or other external means.

Method Two: Dynamic Imports

If you need to dynamically load a module from an external URL at a specific time, you can use ES6's dynamic import syntax. This is not directly implemented through Webpack configuration but is handled at the code level.

Example:

javascript
function loadComponent() {
  return import('https://example.com/external-module.js')
    .then((module) => {
      return module.default;
    })
    .catch(error => 'An error occurred while loading the component');
}

loadComponent().then((component) => {
  // Use the loaded module
});

Note that this requires your environment to support dynamic import syntax or transpile it, and the external resource must allow cross-origin requests.

Method Three: Using Script Tags

The simplest approach is to directly use the <script> tag in your HTML file to include external URLs, and then use these global variables in your JavaScript code. Although this is not implemented through Webpack, it's a straightforward and effective way, especially when dealing with large libraries or frameworks (such as React, Vue, etc.).

Example: In your HTML file:

html
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>

Then, in your JavaScript file, you can directly use $ or jQuery since they are already loaded into the global scope.

Summary

Depending on your specific requirements (such as whether you need to control the loading timing or require dependencies to be loaded from a CDN), you can choose the appropriate method to handle importing resources from external URLs. Typically, using Webpack's externals configuration is the recommended approach for such issues, as it maintains clear module references while avoiding bundling external libraries into the output file.