35 lines
950 B
TypeScript
35 lines
950 B
TypeScript
export type Group<T, TK> = { key: TK; items: T[] };
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declare global {
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interface Array<T> {
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groupBy<T, TK>(keyFn: (item: T) => TK): Group<T, TK>[];
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intersect<T>(other: T[]): T[];
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}
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}
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if (!Array.prototype.groupBy)
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Array.prototype.intersect = function <T>(this: T[], other: T[]): T[] {
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const set = new Set<T>(this);
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return other.filter((i) => set.has(i));
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};
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if (!Array.prototype.groupBy)
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Array.prototype.groupBy = function <T, TK>(
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this: T[],
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keyFn: (item: T) => TK,
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): Group<T, TK>[] {
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const hash = new Map<TK, Group<T, TK>>();
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this.forEach((item) => {
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const key = keyFn(item);
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let group = hash.get(key);
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if (!group) {
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group = { key, items: [] };
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hash.set(key, group);
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}
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group.items.push(item);
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});
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return [...hash.values()];
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};
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export default {};
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