Webpack Academy #1: Loaders

#webpack #webdev #javascript #css

As we saw in the last course, webpack can handle js and json file !

But what happened if we need to import css file ?

Add css file

We need add a new entry point to your application since we have no entry file for css file yet !

webpack.config.js

    entry: {
        myApp: [
            "./src/style.css",
            "./src/main.js",
        ],
    },

style.css

.toto {
    color: blue;
}

Let's go to build this !

ERROR in ./src/style.css 1:0
Module parse failed: Unexpected token (1:0)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
> .toto {
|     color: blue;
| }

What? why?

Loader

As we saw before, webpack only handle js and json file, but webpack let us to use loader, this function is simple -> translate file to webpack in order to handle it !

For handle css file, we will use two loader !

    module: {
        rules: [
            {
                // Match file extension
                test: /\.css$/,
                // Order of loader from bottom to up
                use: [
                    'style-loader',
                    'css-loader'
                ],
            }
        ]
    },

First css-loader will resolve css import issue & return the css (It doesn't actually do anything with the returned CSS), and after style-loader will inject css into the DOM !

So if we add a html file

index.html

<!DOCTYPE html>
<html>
<body>
    <h1 class="toto">My First Heading</h1>

    <p>My first paragraph.</p>
</body>
<script src="dist/bundle.js"></script>
</html>

We can see that your <h1> is blue !

Conclusion

It's just a little example but if you use webpack, you will have a lot of loader, for exemple if you are using ts you will need loader to handle .ts file, if we need to import image we will need another loader etc...

Code here -> https://github.com/Code-Oz/webpack-academy/tree/5e80e4c080c156d1ebd261fc80e3c505d92473a7

I hope you want to learn more about webpack in my academy !

I hope you like this reading!

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