You’ve probably encountered this scenario: you’re setting up a JavaScript project with Webpack 5, and suddenly, functions that were previously accessible everywhere are now undefined when called from the browser. It’s a common frustration, especially when you’re working with JavaScript modules and expecting certain global behaviors in your setup.
Let’s say you’re working on a project organized roughly like this:
my-webpack-project/
├── dist/
│ └── bundle.js
├── src/
│ ├── index.js
│ ├── id_selectors.js
│ ├── button1.js
│ └── button2.js
├── webpack.config.js
└── package.json
Imagine having your functions neatly separated in modules like button1.js, button2.js, and id_selectors.js. You bundle them with Webpack for simpler management. Everything seems great until you notice that a function such as btn2Clicked() throws a “not defined” error when called directly from your HTML.
If you’ve faced this problem, you’re absolutely not alone. Modern Webpack versions handle modules differently—they keep them scoped by default, which means they’re not available globally in the browser. But don’t worry—we’ll solve this together, step by step.
What Exactly is Webpack Doing?
Webpack is a popular module bundler used to compile JavaScript files for better browser compatibility and performance optimization. Instead of loading separate JavaScript files in your HTML, Webpack bundles them into a single file (or multiple optimized chunks).
The main advantages here are better application structure, easy management of dependencies, and fewer HTTP requests, resulting in faster load times.
However, by design, Webpack encapsulates each module to avoid conflicts and pollution of the global scope. Your individual JavaScript files become modules that aren’t accessible directly from your global HTML namespace. This encapsulation can cause issues if you need certain functionalities to be global.
Why Understanding Global Scope is Essential
So, what’s this global scope we keep talking about? Simply put, it’s the top-level context in JavaScript that allows objects or functions to be accessed from anywhere in your app, including HTML event attributes.
Without using Webpack, your JavaScript functions are automatically global, meaning you could easily call onclick="btn2Clicked()" in HTML. But Webpack isolates each module, making every function private unless explicitly attached to the global window object.
To allow these modules to be globally accessible, we’ll need to intentionally expose them, allowing the browser to interact with them directly.
The Key Lies in Webpack Configuration
To solve the issue, let’s first peek into Webpack’s configuration file: webpack.config.js.
Typically, the configuration looks like this:
const path = require('path');
module.exports = {
entry: './src/index.js',
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'dist'),
},
mode: 'development'
};
The entry option specifies the root of your application—where Webpack starts bundling your JavaScript files. Webpack compiles all modules into a single bundle as specified by the output option.
To expose functions globally, we’ll need a slightly different approach—one that explicitly exposes modules to the browser’s global scope.
How to Make Webpack Modules Global
There are a few ways to expose JavaScript modules globally. The most common and clean way is assigning your functions explicitly to the window object. Another common approach is using special Webpack shortcuts or plugins.
Here’s how you explicitly attach modules to the global window object:
- Each JavaScript module that needs a global function exports it explicitly.
- You import these modules in your entry file (typically index.js) and assign the functions explicitly to the global window object.
Let’s walk through the specifics with our example files one by one.
Making id_selectors.js Global
Assume you have utility selectors in this module, something like:
// id_selectors.js
export function selectById(id) {
return document.getElementById(id);
}
Inside your index.js, explicitly attach it to the window object like this:
// index.js
import { selectById } from './id_selectors';
window.selectById = selectById;
After bundling, you can now call selectById() directly from HTML or browser console.
Making button1.js Accessible Globally
Let’s assume button1.js looks like:
// button1.js
export function btn1Clicked() {
alert('Button 1 clicked');
}
Similarly, import and assign it globally in index.js:
// index.js
import { selectById } from './id_selectors';
import { btn1Clicked } from './button1';
window.selectById = selectById;
window.btn1Clicked = btn1Clicked;
Now, calling btn1Clicked() from HTML or console is straightforward and will work as intended.
Making button2.js Global (Resolving Your Original Problem)
Here’s your troubled file:
// button2.js
export function btn2Clicked() {
alert('Button 2 clicked!');
}
Again, just add the function to our window object:
// index.js
import { selectById } from './id_selectors';
import { btn1Clicked } from './button1';
import { btn2Clicked } from './button2';
window.selectById = selectById;
window.btn1Clicked = btn1Clicked;
window.btn2Clicked = btn2Clicked;
That’s it! Rebuild your project with Webpack, and you should no longer encounter “is not defined” errors when calling functions directly from HTML.
Testing the Changes Effectively
After you’ve saved these changes, run your Webpack build again in terminal:
npm run build
Then, open your HTML file in your browser. Click your buttons or trigger functions from the console:
- Open the developer console (press F12).
- Type
btn2Clicked()and hit Enter. - Check if the expected alert or behavior occurs.
You’ll instantly know if your functions are correctly exposed globally.
Additional Considerations and Challenges
Attaching functions to the global window object works fine for small to medium-sized projects. However, for larger, complex apps, it could potentially lead to namespace collisions.
If you’re facing these risks, consider creating a namespaced object on window:
// Creating namespace
window.MyNamespace = {
selectById,
btn1Clicked,
btn2Clicked
};
Then call each method globally as MyNamespace.btn2Clicked().
Another important consideration is Webpack production mode. It might minify or rename your globally-exposed functions. Using correct configuration will ensure stable global naming in both production and development modes.
Key Takeaways from Webpack 5 Global Modules Setup
Webpack is a powerful tool, but you must explicitly expose modules globally if needed. To recap, always:
- Export your modules properly.
- Explicitly attach necessary functions to the global window.
- Thoroughly test after bundling.
- Consider namespaces for larger applications.
By following these guidelines, Webpack 5’s modular encapsulation won’t get in your way. Instead, your JavaScript modules will stay clean, maintainable, and accessible whenever you require global access.
Have you faced other issues using Webpack or global JavaScript modules lately? Share your experiences or questions below—we’d love to hear from you!
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