This is a tiny trick which could be useful when you need to resolve paths and make it in a crossplatform way. This code has no dependencies what makes its' usage extremely simple and cheap. Also such code could migrate from Node.js to a browser without dependencies bundling: no browserify, rollup or whatever is needed.

The trick is in using file: protocol in URL constructor.

Well, let's take an example:

const path = require('path')

const absPath = path.resolve('/some/root', '../index.js')

And replace it with:

const absPath = new URL('../index.js', 'file:///some/root/').pathname

In both cases we receive the same absPath value:

/some/index.js

Note that built-in fs module accepts URLs as paths. Thus in cases when you need to use resolved path within the module, it's possible to just use a URL as argument:

const absPath = new URL('../../hello.txt', 'file:///project/root/')

fs.writeFileSync(absPath, 'Hello, World!')