React hook

useState

useState是最常用的hook了，就不介绍了。
useState可以通过调用callback获取最新的state。方便解决异步调用时获取的state是创建异步时的state而无法获取到最新state的情况。

const [state, setState] = useState(initialState);

useState(lastState=>{
      //get newest state.
      //do something to last state, example: use ... to clone an array or object and modify it.
      return newState;
}

useEffect

useEffect是

useRef

useRef实在是太好用了有木有！！！
useRef类似一个盒子，可以在.current属性里保存任何可变值，不需要类似于useState一样异步存在延迟，屯在最后一次性更新，而是随时随地更新，方便快捷！

    //use useRef to log the audio amplitude of a recording
    const context = new AudioContext();
    const recorder = context.createScriptProcessor(4096, 1, 1);
    recorder.onaudioprocess = function(e) {
      const inputFrame = e.inputBuffer.getChannelData(0);
      const maxvo = Math.max.apply(null, inputFrame);
      if (maxvo > maxVolume.current) 
            maxVolume.current = maxvo;//if use setState, it will log the lastest value bigger than initial value.
    };

    navigator.mediaDevices
      .getUserMedia(mediaConstraints)
      .then(stream => {
        const audioInput = context.createMediaStreamSource(stream);
        audioInput.connect(recorder);
        recorder.connect(context.destination);
      })
      .catch(e => {
        console.error(`Recording Error: ${e}`);
      });

useImperativeHandle

配合ref使用，让父组件也可以时时刻刻获取到子组件的ref。

function FancyInput(props, ref) {
  const inputRef = useRef();
  useImperativeHandle(ref, () => ({
    focus: () => {
      inputRef.current.focus();
    }
  }));
  return <input ref={inputRef} ... />;
}
FancyInput = forwardRef(FancyInput);

//渲染 <FancyInput ref={inputRef} /> 的父组件可以调用 inputRef.current.focus()。

useContent

父组件传给子组件，可以穿透多层子组件。可以父组件用setState更新，子组件也可以随时获取最新值。

      //父组件
      export const StateContext= React.createContext<{
        state: string[];
        setState: (state: string[]) => void;
      }>(null);

          const [state, setState] = useState(null);
          <StateContext.Provider value={{ historyProjects, setHistoryProjects }}>
            <SubComponent />
          </StateContext.Provider>

      //子组件
      const { state, setState} = useContext(StateContext);

自定义Hook

useBoolean

适用于boolean的state。

export function useBoolean(
  initialState: boolean
): [boolean, { setTrue: () => void; setFalse: () => void; toggle: () => void }] {
  const [value, setValue] = useState(initialState);
  const setTrue = () => setValue(true);
  const setFalse = () => setValue(false);
  const toggle = () => setValue(x => !x);
  return [value, { setTrue, setFalse, toggle }];
}

//使用
const [isOpen, { setTrue: openPanel, setFalse: dismissPanel, toggle: togglePanel }] = useBoolean(false);
openPanel();//打开panel
dismissPanel();//关闭panel
togglePanel();//打开时关闭，关闭时打开

useResetState

重置初始状态

export function useResetState<S>(initialState?: S): [S, Dispatch<SetStateAction<S>>, () => void] {
  const [state, setState] = useState(initialState);
  const resetState = () => setState(initialState);
  return [state, setState, resetState];
}

//使用
const [itemToEdit, setItemToEdit, resetItemToEdit] = useResetState(null as TTSProject);
setItemToEdit(item);
resetItemToEdit();//重置成初始状态

记几个好用的hooks

原文：https://www.cnblogs.com/xym4869/p/14049852.html