universal-javascript-runtimes

Use the UnJS toolkit, specifically Nitro and H3, to write universal JavaScript handlers. By configuring Nitro with a specific runtime preset, your single codebase can deploy to both Node.js and edge runtimes without modifications.

Universal JavaScript runtimes solve runtime fragmentation across Node.js, browsers, and edge environments by using adapters and web-standard APIs. They are needed to maintain a single codebase that executes consistently across different deployment targets.

Existing Node.js server code does not automatically work on edge runtimes like Deno and Bun. You must adopt web-standard APIs and use unenv polyfills to bridge the differences and make your code universal.

Configure Nitro presets for cross-platform deployment by targeting a specific runtime in your Nitro configuration file. This allows your H3 handlers and unenv polyfills to compile correctly for Node.js, Deno, Bun, or Cloudflare Workers.

Yes, you can use H3 handlers to create a single API that runs at the edge and on Node servers. H3 abstracts runtime differences, allowing the same code path to execute across various environments without platform-specific maintenance.

Your JavaScript app breaks when moving from Node.js to an edge runtime due to differing APIs. You need to implement unenv polyfills and adopt web-standard APIs to abstract these runtime differences and ensure compatibility.