Redux(1) -手写模拟redux

Redux作为状态管理不仅能在React使用、也能在node等其他地方使用

首先、先来看一段简单的代码

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>

<body>
  <span id="txt"></span>
  <button onclick="dispatch({type:'increment'})">increment</button>
  <script>
    const countState = {
      count: 1
    }

    //渲染页面的函数
    const render = () => {
      let txt = document.getElementById('txt');
      txt.innerHTML = countState.count;
    }

 	//   点击事件的函数
    const dispatch = (action) => {
      //改变数据
      changeState(action)
      //渲染函数
      render();
    }

		//只负责数据的修改
		    const changeState = (action) => {
		    
		      switch (action.type) {
		        case "increment":
		          countState.count += 1;
		          break;
		      }
		      
		    }
		    
    render(); //页面刚打开默认先执行一次

  </script>

</body>

</html>

以上代码的changeState相当于redux中的reducer、只负责修改数据

其次想要把上面函数集中管理

*<button onclick="store.dispatch({type:'increment'})">increment</button>*

  <script>

    const countState = {
      count: 1
    }
    
    const createStore = (reducer) => {

      let state = null;

      const listeners = []      //存储订阅的内容

      const dispatch = (action) => {
        state = reducer(action, state)
        listeners.forEach((listener) => listener())
      }

      const getState = () => {
        return state;
      }
      
      //订阅   当点击的时候给他个通知、他需要一个存储
      const subscribe = (listener) => {
        listeners.push(listener)
      }
      
      dispatch()
      
      return {
        dispatch,
        getState,
        subscribe
      }
    }

    //只负责数据的修改（reducer）
    const changeState = (action, state) => {
      if (!action) {
        return countState;
      }
      switch (action.type) {
        case "increment":
          return {
            count: state.count + 1    //根据redux中state是只读的我们不能直接修改、所以返回一个新值
          }
          break;
      }
    }

    const store = createStore(changeState);

    //渲染函数  
    const render = () => {
      let txt = document.getElementById('txt');
      txt.innerHTML = store.getState().count;
    }
    
    render();

    store.subscribe(render);  //数据只要有改变就调用render

  </script>

至此完成模拟的redux

F_efforts

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