57 lines
1.6 KiB
TypeScript
57 lines
1.6 KiB
TypeScript
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import areInputsEqual from './are-inputs-equal';
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export type EqualityFn<TFunc extends (...args: any[]) => any> = (
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newArgs: Parameters<TFunc>,
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lastArgs: Parameters<TFunc>,
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) => boolean;
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export type MemoizedFn<TFunc extends (this: any, ...args: any[]) => any> = {
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clear: () => void;
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(this: ThisParameterType<TFunc>, ...args: Parameters<TFunc>): ReturnType<TFunc>;
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};
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// internal type
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type Cache<TFunc extends (this: any, ...args: any[]) => any> = {
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lastThis: ThisParameterType<TFunc>;
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lastArgs: Parameters<TFunc>;
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lastResult: ReturnType<TFunc>;
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};
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function memoizeOne<TFunc extends (this: any, ...newArgs: any[]) => any>(
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resultFn: TFunc,
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isEqual: EqualityFn<TFunc> = areInputsEqual,
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): MemoizedFn<TFunc> {
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let cache: Cache<TFunc> | null = null;
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// breaking cache when context (this) or arguments change
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function memoized(
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this: ThisParameterType<TFunc>,
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...newArgs: Parameters<TFunc>
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): ReturnType<TFunc> {
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if (cache && cache.lastThis === this && isEqual(newArgs, cache.lastArgs)) {
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return cache.lastResult;
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}
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// Throwing during an assignment aborts the assignment: https://codepen.io/alexreardon/pen/RYKoaz
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// Doing the lastResult assignment first so that if it throws
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// the cache will not be overwritten
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const lastResult = resultFn.apply(this, newArgs);
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cache = {
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lastResult,
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lastArgs: newArgs,
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lastThis: this,
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};
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return lastResult;
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}
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// Adding the ability to clear the cache of a memoized function
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memoized.clear = function clear() {
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cache = null;
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};
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return memoized;
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}
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export default memoizeOne;
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