Rollup Fundamentals

Introduction

Rollup is a module bundler for JavaScript that compiles small pieces of code into larger, more complex applications. It is particularly known for its ability to optimize the output and reduce the size of the final bundle.

What is Rollup?

Rollup is a JavaScript module bundler that allows developers to write modular code and bundle it into a single file or multiple files for deployment. It uses the ES module syntax to manage dependencies and provides a number of optimizations for production builds.

Key Concepts

Modules: Rollup uses ES6 module syntax to import and export dependencies.
Bundle: The output of Rollup, which contains all the modules and their dependencies.
Plugins: Extend Rollup’s functionality to handle various file types and add features.
Tree-shaking: A feature that eliminates dead code from the final bundle.

Installation

To install Rollup, use npm or yarn:

npm install --save-dev rollup

yarn add --dev rollup

Basic Usage

To create a simple Rollup configuration, create a file named rollup.config.js:

export default {
    input: 'src/main.js',
    output: {
        file: 'dist/bundle.js',
        format: 'iife' // Immediately Invoked Function Expression
    }
};

Then, run Rollup using the command:

npx rollup -c

Advanced Features

Rollup supports advanced features through plugins:

Note: You can find a plethora of plugins for various tasks including Babel transpilation, TypeScript support, and more in the Rollup plugin documentation.

Best Practices

Always use the latest version of Rollup and its plugins.
Utilize tree-shaking to reduce bundle size.
Organize your code into modules for better maintainability.
Keep your rollup.config.js clean and well-commented.

FAQ

What is tree-shaking?

Tree-shaking is a technique used by Rollup to eliminate dead code from the final bundle, ensuring that only the code that is actually used is included.

Can Rollup handle CSS files?

Yes, Rollup can handle CSS files through specific plugins such as rollup-plugin-postcss.

Is Rollup suitable for large applications?

While Rollup is great for libraries and small to medium applications, for very large applications, you might consider using Webpack for its more extensive feature set.