metamask-extension/ui/app/store.js

const createStore = require('redux').createStore
const applyMiddleware = require('redux').applyMiddleware
const thunkMiddleware = require('redux-thunk')
const rootReducer = require('./reducers')
const developmentMode = require('../../app/scripts/config').developmentMode
const createLogger = require('redux-logger')

module.exports = configureStore

const middlewares = [thunkMiddleware]

if (developmentMode) {
  const loggerMiddleware = createLogger()
  middlewares.push(loggerMiddleware)
}

const createStoreWithMiddleware = applyMiddleware(...middlewares)(createStore)

function configureStore (initialState) {
  return createStoreWithMiddleware(rootReducer, initialState)
}