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35 lines
815 B
JavaScript
35 lines
815 B
JavaScript
import { useEffect, useRef } from 'react';
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/**
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* Runs an effect only when the dependencies have changed, skipping the
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* initial "on mount" run. Caution, if the dependency list never changes,
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* the effect is **never run**
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*
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* ```ts
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* const ref = useRef<HTMLInput>(null);
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*
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* // focuses an element only if the focus changes, and not on mount
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* useUpdateEffect(() => {
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* const element = ref.current?.children[focusedIdx] as HTMLElement
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*
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* element?.focus()
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*
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* }, [focusedIndex])
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* ```
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* @param effect An effect to run on mount
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*
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* @category effects
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*/
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function useUpdateEffect(fn, deps) {
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var isFirst = useRef(true);
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useEffect(function () {
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if (isFirst.current) {
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isFirst.current = false;
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return;
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}
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return fn();
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}, deps);
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}
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export default useUpdateEffect; |