const asyncFunction = () => { api.fetchObjects() .then((result) => { setObjects(objects => [ ...objects, // <-- shallow copy previous state array result, // <-- append new state ]); }); } 或使用async/await const asyncFunction = async () => { const result = await api....
we didn't mutate `items` > items === clone false // these are different objects > items[0] === clone[0] true // we don't need to clone items 0 and 2 because we're not mutating them (efficiency gains!) > items[1] === clone[1] false // this guy we copied 原文由 mpen ...
例如// generalthis.setState((oldState) => ({ ...oldState }));// useful for updating objec...
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So instead of the call happening three times, it happens just once. This can be fixed by passing a function tosetState(). Just as you pass objects tosetState(), you can also pass functions, and that is the way out of the situation above. ...
Also, I can't think of many situations where you really would want to wait for setState to propagate before calling that parent callback ... In my case, I wanted to wait for the re-render, because afterward I can operate on arefwhich would be hidden before due a conditional rendering....
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@akhileshkcoderIn your case, you are mutating the nthtodowhentodo.id === id, so, even thoughnewtodosis a new array when you return the next state atreturn {todos: newtodos}, yoursetStatecallback function is not pure. Try this instead: ...
)} {console.log(typeof this.st...