ModLib

Use ES6 modules from npm in webapps without transpiling.

ModLib is a tool class, to create a library out of the ES6 modules of node_modules packages to use them in web apps.

The problem with ES6 and npm in web projects

Let's assume we have two ES6 projects. "cm-main" and "cm-dependency" with the following structure: cm-main/src/Main.js and cm-dependency/src/Dependency.js.

When developing "cm-main" the import path from src/Main.js to node_modules/cm-dependency/src/Dependency.js would be ../node_modules/cm-dependency/src/Dependency.js but later when both are npm packages, they are both in node_modules and then the import path will become ../../cm-dependency/Dependency.js. Because of that importing files from node_modules does not work for ES6 web-projects.

The solution (without transpiling)

When we copy node_modules/cm-dependency/src/Dependency.js to lib/Dependency.js on npm install, the include path for local development from src/Main.js will be ../lib/Dependency.js. And later, when both are npm packages, the import path from lib/Main.js will remain ../lib/Dependency.js. 👍

Usage

ModLib is mainly used in postinstall.cjs.

// Create an instance of `ModLib` in your `postinstall.cjs`:

const modLib = new (require("modlib"))

// Then add modules from packages

modLib.add("npm-package-name-1")
modLib.add("npm-package-name-2")
// [..]

The module sources will be copied from the node_modules/package/src/* to the lib/package/* folder for easy handling of the relative import path from other ES6 modules.

Auto execute postinstall.cjs on npm install with adding it to your package.json like so

"scripts": {
  "postinstall": "node postinstall.cjs"
}

Examples

It works in these plain ES6 module based apps and components, which must not be transpiled or compiled to run. They work out of the box without transpiling, without babel.

• cm-chess
• cm-fen-editor
• chess-console
• chess-console-stockfish

API

constructor

/**
 * @param projectRoot Your project root, mostly `__dirname`
 * @param props Configuration properties
 */
constructor(projectRoot = __dirname, props = {})

Default props

props = {
    nodeModulesPath: path.resolve(__dirname, '../../'), // path to `node_modules`
    libraryFolder: "lib", // library folder where the module sources are linked/copied to
    mode: "copy" // set to "symlink" to symlink sources instead of copying
}

method add to a package to the library

/**
 * Add the modules of a node package to the library
 * @param packageName Name of the nmp package
 * @param projectSourceRoot The source root inside the package folder
 * @param fileOrFolder The module source folder or file inside the 'projectSourceRoot'
 */
add(packageName, projectSourceRoot = "src", fileOrFolder = packageName)