withHandlers.js

import { Component } from 'react'
import createEagerFactory from './createEagerFactory'
import createHelper from './createHelper'

const mapValues = (obj, func) => {
  const result = []
  let i = 0
  /* eslint-disable no-restricted-syntax */
  for (const key in obj) {
    if (obj.hasOwnProperty(key)) {
      i += 1
      result[key] = func(obj[key], key, i)
    }
  }
  /* eslint-enable no-restricted-syntax */
  return result
}

const withHandlers = handlers => BaseComponent => {
  const factory = createEagerFactory(BaseComponent)
  let cachedHandlers
  let handlers
  
  return props => {
    cachedHandlers = {}
    handlers = handlers || mapValues(
      handlers,
      (createHandler, handlerName) => (...args) => {
        const cachedHandler = cachedHandlers[handlerName]
        if (cachedHandler) {
          return cachedHandler(...args)
        }

        const handler = createHandler(props)
        cachedHandlers[handlerName] = handler

        if (
          process.env.NODE_ENV !== 'production' &&
          typeof handler !== 'function'
        ) {
          console.error(
            'withHandlers(): Expected a map of higher-order functions. ' +
            'Refer to the docs for more info.'
          )
        }

        return handler(...args)
      }
    )
    
    return factory({
      ...props,
      ...handlers
    })
  }
}

export default createHelper(withHandlers, 'withHandlers')