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📜  useEffect time elapsed - Javascript 代码示例

📅  最后修改于: 2022-03-11 15:02:28.411000             🧑  作者: Mango

代码示例1
const Clock = ({ dispatch, inProgress, ticksElapsed }) => {
  React.useEffect(() => {
    const progressTimer = setInterval(function () {
      inProgress && dispatch({ type: 'CLOCK_RUN' });
    }, 500);
    return () =>
      //inprogress is stale so when it WAS true
      //  it must now be false for the cleanup to
      //  be called
      inProgress && clearInterval(progressTimer);
  }, [dispatch, inProgress]);

  return 

{ticksElapsed}

; }; const App = () => { const [inProgress, setInProgress] = React.useState(false); const [ticksElapsed, setTicksElapsed] = React.useState(0); const dispatch = React.useCallback( () => setTicksElapsed((t) => t + 1), [] ); return (
); }; ReactDOM.render(, document.getElementById('root'));