Скачать или смотреть Resolve the undefined Issue with Less in TypeScript and Webpack

Learn how to fix the `undefined` problem when importing Less files in your TypeScript and Webpack setup. Follow these simple steps to configure your build process effectively!
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This video is based on the question https://stackoverflow.com/q/73854643/ asked by the user 'Up Pu' ( https://stackoverflow.com/u/19556200/ ) and on the answer https://stackoverflow.com/a/73855652/ provided by the user 'Criwran' ( https://stackoverflow.com/u/11523294/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the undefined Issue when Importing Less Files in TypeScript Using Webpack

If you’re working with TypeScript and Webpack and have encountered the frustrating issue of getting undefined when trying to import Less styles, you’re not alone. This issue can arise even when the Less file is correctly referenced and exists in your project directory. Let’s explore how to properly configure your setup to resolve this issue effectively.

Understanding the Problem

In your TypeScript file src/pages/login/index.tsx, you've imported styles from a Less file (index.less), but you find that the imported styles variable is undefined. Here’s the relevant code snippet:

[[See Video to Reveal this Text or Code Snippet]]

You might check that your index.less contains the required styles:

[[See Video to Reveal this Text or Code Snippet]]

Cause of the Issue

The main cause of the problem is found in your Webpack configuration. Specifically, the way you have set up the CSS loader for Less files doesn’t allow modules to be recognized correctly, which is essential for scoped styles in a modular environment like React.

Solution Steps

To resolve the issue, you'll need to update the Webpack configuration to enable CSS modules for Less files. Follow these simple steps:

1. Update Your Webpack Configuration

Locate the existing rule for Less files in your Webpack config file. It should look something like this:

[[See Video to Reveal this Text or Code Snippet]]

2. Change the modules Option

Change the modules option from false to true as shown below:

[[See Video to Reveal this Text or Code Snippet]]

3. Save and Rebuild

After making this change, save your Webpack configuration file and rebuild your project. The styles variable in your index.tsx should now correctly reference the compiled styles from index.less, and you should no longer see undefined in the console log.

4. Verify Your Changes

To confirm that everything is working correctly, run your application and check that the styles are applied as expected. Your Login Page should now display with the defined styles from your Less file.

Conclusion

By simply adjusting the Webpack configuration to properly enable CSS modules for Less files, you can resolve the undefined issue when importing styles in your TypeScript project. This setup ensures that your styles are correctly scoped and applied, allowing for a more modular and maintainable codebase. Happy coding!