Rollup.js is a popular JavaScript bundler that helps optimize the size and performance of front-end applications. One common pain point when working with Rollup.js is the build time, especially for larger projects. In this blog post, we will explore two techniques to improve Rollup.js build speed: parallel builds and caching.

Parallel Builds

By default, Rollup.js performs a sequential build process, which means it processes one module at a time. This can be a bottleneck when dealing with large codebases. Luckily, Rollup.js provides an option to enable parallel builds, which can significantly speed up the build process.

To enable parallel builds, you need to install the rollup-plugin-parallel plugin. To do this, run the following command:

npm install rollup-plugin-parallel --save-dev

Once installed, you can configure Rollup.js to use parallel builds by adding the following code to your rollup.config.js file:

import parallel from 'rollup-plugin-parallel';

export default {
  // ... other Rollup.js configuration options
  plugins: [
    // ... other plugins
    parallel({ /* options */ }),
  ],
};

The rollup-plugin-parallel plugin allows you to specify various options to control the parallel build behavior. For example, you can configure the maximum number of parallel workers and specify which file extensions to process in parallel. Experiment with different options to find the optimal configuration for your project.

Caching

Another technique to improve Rollup.js build speed is to leverage caching. Caching allows Rollup.js to skip re-processing modules that haven’t changed since the last build. This helps avoid unnecessary work and reduces the overall build time.

To enable caching in Rollup.js, you need to install the rollup-plugin-node-resolve and rollup-plugin-json plugins. Run the following command to install them:

npm install rollup-plugin-node-resolve rollup-plugin-json --save-dev

Once installed, modify your rollup.config.js file as follows:

import resolve from 'rollup-plugin-node-resolve';
import json from 'rollup-plugin-json';

export default {
  // ... other Rollup.js configuration options
  plugins: [
    // ... other plugins
    resolve(),
    json(),
  ],
  cache: true,
};

By adding the cache: true option to the Rollup.js configuration, you enable caching. The rollup-plugin-node-resolve plugin helps resolve and cache external dependencies, while the rollup-plugin-json plugin enables caching of JSON modules.

Keep in mind that caching is only effective if your codebase hasn’t changed. If you modify any module, Rollup.js will regenerate the bundle from scratch. However, for subsequent builds without code changes, caching will significantly improve build speed.

Conclusion

Improving Rollup.js build speed can greatly enhance development productivity, especially when working on large projects. By using parallel builds and caching techniques, you can reduce build times and iterate faster. Remember to experiment with different configurations to find what works best for your specific project.

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