First, we need an entry point. Note that when a relative path is directly marked as "external" using the external option, then it will be the same relative path in the output. You've created your first bundle with Rollup. Paste this into a new file called src/main.js: // src/main.js import foo from './foo.js'; export default function () { console.log(foo); } Determines after how many runs cached assets that are no longer used by plugins should be removed. See also Reading a file from stdin. Warnings objects have, at a minimum, a code and a message property, allowing you to control how different kinds of warnings are handled. Type: string | RegExp | (string | RegExp)[] CLI: --watch.exclude , Type: string | RegExp | (string | RegExp)[] CLI: --watch.include . Rebuild the bundle with ./node_modules/.bin/rollup -c, then check the browser again to see the output: Environment variables add a lot of power to our development flow, and give us the ability to do things such as turning logging off and on, injecting dev-only scripts, and more. Because we didn't specify an output file, it will be printed straight to stdout: You can save the bundle as a file like so: (You could also do rollup src/main.js -f cjs > bundle.js, but as we'll see later, this is less flexible if you're generating sourcemaps.). One possible use-case is minification of bundles to be consumed in a browser. But at the moment, the majority of packages on NPM are exposed as CommonJS modules instead. If a plugin wants to retain resources across builds in watch mode, they can check for this.meta.watchMode in this hook and perform the necessary cleanup for watch mode in closeWatcher. Let's add a simple dependency called the-answer, which exports the answer to the question of life, the universe and everything: The resulting bundle.js will still work in Node.js, because the import declaration gets turned into a CommonJS require statement, but the-answer does not get included in the bundle. For example, given the following configuration: The preserveModulesRoot setting ensures that the input modules will be output to the paths dist/module.js and dist/another/module.js. (For example, it's pretty common to see this used to assign default values, like var value = maybeThisExists || 'default'.). If the type is chunk, then this emits a new chunk with the given module id as entry point. commonjs(), not just commonjs). Other properties are added depending on the type of warning. Powered by GitBook. Emitted assets will follow the output.assetFileNames naming scheme. Adding this property is a standard implemented by Rollup, Babel and many other tools to signify that the required value is the namespace of a transpiled ES module: Note how Rollup is reusing the created namespace object to get the default export. : boolean | "no-treeshake" | null, syntheticNamedExports? For example, with -f es for native modules: Or alternatively, for SystemJS with -f system: And then load either or both entry points in an HTML page as needed: See rollup-starter-code-splitting for an example on how to set up a web app that uses native ES modules on browsers that support them with a fallback to SystemJS if necessary. In-lined source maps (a source map where the content is stored as a data URL instead of a separate file) are also supported, although in-lined source is not yet supported. 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