babel-plugin-bundled-import-meta

Babel plugin to rewrite import.meta.url for use in bundles.

Install babel-plugin-bundled-import-meta

This module requires node.js 10 or above and @babel/core.

npm i babel-plugin-bundled-import-meta

Usage

Add babel-plugin-bundled-import-meta to plugins in your babel settings.

Settings

{
	"plugins": [
		["babel-plugin-bundled-import-meta", {
			"mappings": {
				"node_modules": "/assets"
			},
			"bundleDir": "html"
		}]
	]
}

This example will assume that html/ will directly contain the bundled JavaScript. node_modules/ served from /assets. Any use of import.meta outside these two folders will throw an exception.

bundleDir

If no mappings match it is assumed that bundleDir is served from the same directory as the output bundle. In the example where bundleDir is set to html it is assumed that assets in html/components will be published in ./components relative to the bundled JavaScript.

Default process.cwd().

mappings

This maps source paths to server URL's. Key's represent local source paths, values represent base URL which would be used for the unbundled build. Value URL's can be relative or absolute. Relative URL's will be resolved at runtime using the bundle URL as the base URL.

Default {}.

importStyle

It's necessary to know the full URL of the bundle as loaded by the browser. The best way to determine this is different based on what type of bundle will be used.

Supported styles are: amd, cjs, esm, iife, umd, system. Default esm.

The esm import style generates import.meta.url to detect the bundled URL. This is not compatible with webpack so use another method. If anyone knows of a 'best' option for use with webpack please open an issue or PR.

When bundling with rollup you should generally use esm here. The only exception is if rollup is generating an esm bundle for targets that do not support import.meta.url. If you are using import.meta.url in your code but must maintain compatibility with browsers that do not support this it is probably best to have rollup generate a different bundle format.

Attribution

This module is based on code found in polymer-build.