metamask-extension/ui/app/ducks/locale/locale.js

import * as actionConstants from '../../store/actionConstants'

export default function reduceLocaleMessages (state = {}, { type, value }) {
  switch (type) {
    case actionConstants.SET_CURRENT_LOCALE:
      return {
        ...state,
        current: value.messages,
      }
    default:
      return state
  }
}

export const getCurrentLocaleMessages = (state) => state.localeMessages.current

export const getEnLocaleMessages = (state) => state.localeMessages.en