41 lines
1.4 KiB
Plaintext
41 lines
1.4 KiB
Plaintext
import areInputsEqual from './are-inputs-equal';
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// Using ReadonlyArray<T> rather than readonly T as it works with TS v3
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export type EqualityFn = (newArgs: any[], lastArgs: any[]) => boolean;
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function memoizeOne<
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// Need to use 'any' rather than 'unknown' here as it has
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// The correct Generic narrowing behaviour.
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ResultFn extends (this: any, ...newArgs: any[]) => ReturnType<ResultFn>
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>(resultFn: ResultFn, isEqual: EqualityFn = areInputsEqual): ResultFn {
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let lastThis: unknown;
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let lastArgs: unknown[] = [];
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let lastResult: ReturnType<ResultFn>;
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let calledOnce: boolean = false;
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// breaking cache when context (this) or arguments change
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function memoized(this: unknown, ...newArgs: unknown[]): ReturnType<ResultFn> {
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if (calledOnce && lastThis === this && isEqual(newArgs, lastArgs)) {
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return 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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// nothing will be overwritten
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lastResult = resultFn.apply(this, newArgs);
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calledOnce = true;
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lastThis = this;
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lastArgs = newArgs;
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return lastResult;
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}
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return memoized as ResultFn;
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}
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// default export
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export default memoizeOne;
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// disabled for now as mixing named and
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// default exports is problematic with CommonJS
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// export { memoizeOne };
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