11 lines
267 B
TypeScript
11 lines
267 B
TypeScript
export default function groupBy<K, V>(arr: V[], fn: (v: V) => K): Map<K, V[]> {
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const map = new Map<K, V[]>();
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arr.forEach(e => {
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const key = fn(e);
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if (!map.has(key)) {
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map.set(key, [] as V[]);
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}
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map.get(key)!.push(e);
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});
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return map;
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} |