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43 lines
1.1 KiB
JavaScript
43 lines
1.1 KiB
JavaScript
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import { useRef } from 'react';
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function isEqual(a, b) {
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if (a.length !== b.length) return false;
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for (var i = 0; i < a.length; i++) {
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if (a[i] !== b[i]) {
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return false;
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}
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}
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return true;
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}
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/**
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* Identical to `useMemo` _except_ that it provides a semantic guarantee that
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* values will not be invalidated unless the dependencies change. This is unlike
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* the built in `useMemo` which may discard memoized values for performance reasons.
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*
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* @param factory A function that returns a value to be memoized
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* @param deps A dependency array
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*/
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export default function useStableMemo(factory, deps) {
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var isValid = true;
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var valueRef = useRef(); // initial hook call
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if (!valueRef.current) {
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valueRef.current = {
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deps: deps,
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result: factory()
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}; // subsequent calls
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} else {
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isValid = !!(deps && valueRef.current.deps && isEqual(deps, valueRef.current.deps));
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}
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var cache = isValid ? valueRef.current : {
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deps: deps,
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result: factory()
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}; // must update immediately so any sync renders here don't cause an infinite loop
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valueRef.current = cache;
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return cache.result;
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}
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