change-emitter

Listen for changes. Like an event emitter that only emits a single event type. Really tiny.

I extracted this from Redux's createStore() because I found it to be useful in other contexts. Use it where you want the most minimal event subscription implementation possible.

Usage

1import { createChangeEmitter } from 'change-emitter'
2
3const emitter = createChangeEmitter()
4
5// Called `listen` instead of `subscribe` to avoid confusion with observable spec
6const unlisten = emitter.listen((...args) => {
7  console.log(args)
8})
9
10emitter.emit(1, 2, 3) // logs `[1, 2, 3]`
11unlisten()
12emitter.emit(4, 5, 6) // doesn't log

Larger example

Here's a (partial) implementation of Redux's createStore:

1const createStore = (reducer, initialState) => {
2  let state = initialState
3  const emitter = createChangeEmitter()
4
5  function dispatch(action) {
6    state = reducer(state, action)
7    emitter.emit()
8    return action
9  }
10
11  function getState() {
12    return state
13  }
14
15  return {
16    dispatch,
17    getState,
18    subscribe: emitter.listen
19  }
20}