Redux Counter example

此项目模板是使用Create React App构建的，它提供了一种简单的方法来启动React项目而无需构建配置。
使用Create-React-App构建的项目包括对ES6语法的支持，以及几种非官方/尚未最终形式的Javascript语法，
先看效果

分析代码为
1.入口文件

import React from 'react'
import ReactDOM from 'react-dom'
//引入redux
import { createStore } from 'redux'
//入口引入组件
import Counter from './components/Counter'
//引入reducer
import counter from './reducers'

const store = createStore(counter)
const rootEl = document.getElementById('root')
  // 通过dispatch一个action来set state
const render = () => ReactDOM.render(
  <Counter
    value={store.getState()}
    onIncrement={() => store.dispatch({ type: 'INCREMENT' })}
    onDecrement={() => store.dispatch({ type: 'DECREMENT' })}
  />,
  rootEl
)

render()
//订阅subscribe
store.subscribe(render)

reducer纯函数

//reducer.js
//纯函数state改变
export default (state = 0, action) => {
  switch (action.type) {
    case 'INCREMENT':
      return state + 1
    case 'DECREMENT':
      return state - 1
    default:
      return state
  }
}

//counter组件
import React, { Component } from 'react'
import PropTypes from 'prop-types'

class Counter extends Component {
  constructor(props) {
    super(props);
    this.incrementAsync = this.incrementAsync.bind(this);
    this.incrementIfOdd = this.incrementIfOdd.bind(this);
  }

  incrementIfOdd() {
    if (this.props.value % 2 !== 0) {
      this.props.onIncrement()
    }
  }

  incrementAsync() {
    setTimeout(this.props.onIncrement, 1000)
  }

  render() {
    const { value, onIncrement, onDecrement } = this.props
    return (
      <p>
        Clicked: {value} times
        {' '}
        <button onClick={onIncrement}>
          +
        </button>
        {' '}
        <button onClick={onDecrement}>
          -
        </button>
        {' '}
        <button onClick={this.incrementIfOdd}>
          Increment if odd
        </button>
        {' '}
        <button onClick={this.incrementAsync}>
          Increment async
        </button>
      </p>
    )
  }
}

Counter.propTypes = {
  value: PropTypes.number.isRequired,
  onIncrement: PropTypes.func.isRequired,
  onDecrement: PropTypes.func.isRequired
}

export default Counter