resolve-url-modern

A maintained, compatibility-first continuation of the deprecated resolve-url browser library.

The public API remains one function, resolveUrl(...urls). It resolves every argument from left to right using the browser's URL behavior. This is not a general-purpose Node.js URL resolver.

Compatibility policy

Existing behavior wins over internal novelty. Changes are checked in real Chromium, Firefox, and WebKit against a licensed copy of the 0.2.1 implementation. See COMPATIBILITY.md for details.

Install

npm install resolve-url-modern

The package has no runtime dependencies and no build step.

CommonJS

Use the CommonJS export in browser-targeted code or a browser bundle:

var resolveUrl = require("resolve-url-modern")

resolveUrl("/static/scripts/app.js", "../source-maps/app.js.map")
// https://example.com/static/source-maps/app.js.map

Requiring the module in Node.js returns the function, but calling it needs a browser document. Node.js-only execution is not a supported runtime API.

Browser global and AMD

The distributed file can be loaded directly as a classic script:

<script src="resolve-url.js"></script>
<script>
  resolveUrl("remove")
</script>

The global name is resolveUrl. The same file retains its original AMD define(factory) branch.

API: resolveUrl(...urls)

Pass one or more URL values. The first value is resolved against the document's used base URL. Each later value is resolved against the previous result. The final string is returned.

resolveUrl(
  "/static/scripts/app.js",
  "../source-maps/app.js.map",
  "../coffee/app.coffee"
)
// https://example.com/static/coffee/app.coffee

Calling resolveUrl() with no arguments throws:

Error: resolveUrl requires at least one argument; got none.

Values are converted to strings by browser DOM URL properties, as in the original package.

Browser support

Compatibility is tested with the Chromium, Firefox, and WebKit versions bundled by the locked Playwright release. The package no longer claims the original IE 8, Opera 12, or Safari 5 matrix.

Migration from resolve-url

Usually only the dependency and import name change:

-var resolveUrl = require("resolve-url")
+var resolveUrl = require("resolve-url-modern")

After publication and registry verification, an npm alias can keep source imports unchanged:

{
  "dependencies": {
    "resolve-url": "npm:resolve-url-modern@^0.3.0"
  }
}

ESM

There is no separate ESM entry point. Keeping CommonJS, AMD, and browser-global interfaces avoids a build pipeline. ESM consumers should use their runtime or bundler's CommonJS interop.

Known differences

Version 0.3.0 keeps the original resolver implementation, so no result differences are accepted. Package metadata, development tooling, browser coverage, and documentation changed. MODERNIZATION.md explains why the first WHATWG URL candidate was not shipped.

Development

npm install
npx playwright install chromium firefox webkit
npm test

The suite runs Golden Master and differential checks in all three engines.

License

MIT. Simon Lydell's original copyright notice is retained in LICENSE and the copied fixture.