ESMitter

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Compatibility ​

ESMitter is a fork of the popular EventEmitter3, but natively TypeScript, ESM-only and with more modern tooling. The complete codebase has been converted to TypeScript and EcmaScript module syntax (ESM). ESMitter is currently less performant than EventEmitter3, but still fast with millions of operations per second.

Compatibility with Node.js' EventEmitter ​

The module is API compatible with the EventEmitter that ships by default with Node.js but there are some slight differences:

  • Domain support has been removed.
  • We do not throw an error when you emit an error event and nobody is listening.
  • The newListener and removeListener events have been removed as they are useful only in some uncommon use-cases.
  • The setMaxListeners, getMaxListeners, prependListener and prependOnceListener methods are not available.
  • Support for custom context for events so there is no need to use fn.bind.
  • The removeListener method removes all matching listeners, not only the first.

Compatibility with EventEmitter3 ​

ESMitter is designed to be a drop-in replacement for EventEmitter3, maintaining compatibility with its API. Unlike EventEmitter3, ESMitter is strongly typed, so while your function calls can remain unchanged, you will need to provide type definitions for your events.

Known incompatibilities with EventEmitter3 ​

  • The listenerCount() method requires an event name as the first argument and will thus not return the number of listeners for all events combined.

Benchmarks ​

The EventEmitter3 library comes with benchmarks that compare its performance with some available alternatives. The results can be found here: https://github.com/tillsanders/esm-itter/blob/main/benchmarks/README.md

Compatibility with Deno ​

ESMitter is fully compatible with Deno, as it is written in TypeScript and uses EcmaScript modules. It is available via the jsr.io registry, allowing you to seamlessly import it in your Deno projects.