Redux in <1kb

µredux.js

var INIT = '@redux/INIT'

function createStore (reducer, state, enhancer) {
  if (enhancer) return enhancer(createStore)(reducer, state)

  var subscribers = []

  dispatch({ type: INIT })

  return {
    subscribe: subscribe,
    dispatch: dispatch,
    getState: getState,
    replaceReducer: replaceReducer
  }

  function subscribe (listener) {
    subscribers.push(listener)
    var idx = subscribers.length - 1
    return function unsubscribe () {
      delete subscribers[idx]
    }
  }

  function dispatch (action) {
    state = reducer(state, action)
    subscribers.forEach(function (fn) { fn() })
  }

  function getState () {
    return state
  }

  function replaceReducer (next) {
    reducer = next
    dispatch({ type: INIT })
  }
}