Abstract:
This post covers troubleshooting common Webpack issues encountered during frontend development. It explains how to resolve problems like double script loading, which can occur from conflicting manual script imports and Webpack configuration, and how to fix Flash of Unstyled Content (FOUC) by correctly setting production mode using cross-env and properly configuring the MiniCssExtractPlugin for CSS handling.
Estimated reading time: 2 minutes
Webpack is a tool that helps manage and bundle the code for websites. Here’s a brief summary of what Webpack is:
Webpack is an open-source JavaScript module bundler. It was initially released on March 10, 2012, by Tobias Koppers. Webpack is designed to bundle JavaScript files for usage in a browser, yet it is also capable of transforming, bundling, or packaging just about any resource or asset. It allows developers to bundle their JavaScript applications into a single file or split them into chunks that can be loaded on demand, improving the performance of web applications.
Webpack processes your application by starting from one or more entry points and then finding all dependencies, creating a dependency graph. It then bundles all these dependencies into static assets. It’s highly extensible via loaders and plugins, allowing it to handle not only JavaScript but also HTML, CSS, images, and more by converting them into valid modules.
Be careful with how your JavaScript is being bundled and added to your HTML by Webpack. My app was behaving strangely – some things happened twice! After checking the HTML file created by Webpack (in the dist folder), I saw the same script was being imported two times.
This happened because I was manually adding the JavaScript file in my index.html file, like this:
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<script src="dist/bundle.js"></script>
And Webpack was also set to load the same script in its configuration file (webpack.config.js):
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entry: './src/main.js', // Adjust this to the path of your main JS file
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'dist'),
},
Another tip: If you see a FOUC (Flash of Unstyled Content), where your page loads without styles for a moment, carefully check how Webpack is building and preparing your project. Make sure production mode is being set correctly.
My package.json build command was previously:
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"build": "webpack --mode production",
But this was not correctly handling my CSS file because production mode was not being recognized properly. I fixed it by using cross-env:
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"build": "cross-env NODE_ENV=production webpack --mode production",
This solution depends on the following code in the webpack.config.js file:
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plugins: [
// ... other plugins
...(process.env.NODE_ENV === 'production' ? [new MiniCssExtractPlugin()] : []),
// ... other plugins
],
This creates a main.css file in the dist folder. This CSS file is then correctly loaded early in the <head> section of my index.html file (also in the dist folder), preventing FOUC.
