prevents v1.0.3

prevents

Wrap an EventEmitter for easy listener cleanup

Usage

npm install prevents

var wrap = require('prevents')

// wrap an EventEmitter called `emitter`
var wrapper = wrap(emitter)

// wrapper has all of the EventEmitter methods
// and receives all events emitted by `emitter`
wrapper.on(...)
wrapper.once(...)
wrapper.removeListener(...)
...

// when done, remove all listeners on `wrapper`
// (leaving `emitter` untouched)
wrapper.removeAll()

prevents lets you wrap an EventEmitter, letting you add/remove listeners to a separate EventEmitter without polluting the original. When you are done, you can clean up all of the listeners added to the wrapper EventEmitter.

API

var wrapper = wrap(emitter)

Creates a wrapper EventEmitter which receives all events emitted by emitter.

The returned object has all EventEmitter methods (e.g. wrapper.on(event, listener)). Calling wrapper.emit(event, listener) will only emit the event to the listeners added directly to the wrapper, not the wrapped emitter.

wrapper.removeAll()

Removes all listeners added directly to wrapper.

Rationale

I often found myself in a code pattern where I would temporarily add event listeners to some EventEmitter, then need to remove them all when done. However, this requires keeping a reference to all listener functions so that they can be removed with removeListener(), which can be inconvenient. It also makes it possible to accidentally leak listeners if they never got removed.

This module makes this use-case easy: in a function where you add temporary listeners, wrap the EventEmitter and add the listeners to it, then call removeAll() when done to ensure all listeners are cleaned up.