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useStableMemo.js
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Created: Mon, Feb 3, 09:50

useStableMemo.js
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	import { useRef } from 'react';

	function isEqual(a, b) {
	if (a.length !== b.length) return false;

	for (var i = 0; i < a.length; i++) {
	if (a[i] !== b[i]) {
	return false;
	}
	}

	return true;
	}

	/**
	* Identical to `useMemo` _except_ that it provides a semantic guarantee that
	* values will not be invalidated unless the dependencies change. This is unlike
	* the built in `useMemo` which may discard memoized values for performance reasons.
	*
	* @param factory A function that returns a value to be memoized
	* @param deps A dependency array
	*/
	export default function useStableMemo(factory, deps) {
	var isValid = true;
	var valueRef = useRef(); // initial hook call

	if (!valueRef.current) {
	valueRef.current = {
	deps: deps,
	result: factory()
	}; // subsequent calls
	} else {
	isValid = !!(deps && valueRef.current.deps && isEqual(deps, valueRef.current.deps));
	}

	var cache = isValid ? valueRef.current : {
	deps: deps,
	result: factory()
	}; // must update immediately so any sync renders here don't cause an infinite loop

	valueRef.current = cache;
	return cache.result;
	}

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