Module Bundler

The most basic function of module bundlers like Webpack and Rollup are to combine the source files and dependencies into one large bundle. Newer technologies and features have been added on top of this, like Code Splitting to optimize performance instead of serving a large single bundle script. Most of them also include loaders: preprocessors that can process other files into JS. Like the style-loader or the scss loaders to convert Sass to CSS. They almost always feature a plugin system, like for frameworks like Vue and React. Some also have the feature to start a dev web server to watch for changes in files and serve a development build of the website.