/
utils.ts
33 lines (32 loc) · 972 Bytes
/
utils.ts
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export function groupByCallback<T, K>(
values: readonly T[],
callback: (value: T) => K,
// tslint:disable-next-line:readonly-array readonly-keyword
): { readonly key: K; values: T[] }[] {
return values.reduce(
(grouped, value) => {
const key = callback(value);
const existing = grouped.find(group => group.key === key);
if (existing) {
existing.values.push(value);
} else {
grouped.push({
key: key,
values: [value],
});
}
return grouped;
},
// tslint:disable-next-line:readonly-array readonly-keyword
[] as { readonly key: K; values: T[] }[],
);
}
export function maxWithComparatorCallback<T>(
values: readonly T[],
callback: (value1: T, value2: T) => number,
): T {
if (values.length === 0) throw new Error("No values to compare");
return values
.slice(1)
.reduce((previous, next) => (callback(previous, next) > 0 ? previous : next), values[0]);
}