node-repl-polyfill

Simple node:repl polyfill for other JS runtimes which do not support node:repl (eg Deno, Bun).

This polyfill does not aim to have full parity but provide a basic library for people wanting to use the basics of node:repl. The default eval function is intentionally terrible, as it is expected you are bringing your own. With these limitations, it should act like a "drop-in" replacement for node:repl by just importing this package instead of node:repl. This package does no detection for native support of node:repl, so does not try to use a native implementation at all.

npm install node-repl-polyfill

Recommended import

You can use the following import as to use node:repl if supported by the runtime being used:

let repl;
try {
  // try importing node:repl
  repl = await import('node:repl');

  // check it is not just a mock with REPLServer prototype
  if (repl.REPLServer.prototype.defineCommand == null)
    throw 'mock node:repl detected';
} catch {
  // it failed, import the polyfill
  repl = (await import('node-repl-polyfill')).default;
}

Runtime requirements

This polyfill relies on the runtime supporting:

• node:process (stdin, stdout)
• node:util (inspect)
• node:readline (Interface)

Runtimes tested:

• Node (20.12.0)
• Deno (1.42.2)
• Bun (1.1.5)