59 lines
1.9 KiB
TypeScript
59 lines
1.9 KiB
TypeScript
/*
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Copyright 2020 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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export function groupBy<K, V>(array: V[], groupFn: (V) => K): Map<K, V[]> {
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return groupByWithCreator<K, V, V[]>(array, groupFn,
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() => {return [];},
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(array, value) => array.push(value)
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);
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}
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export function groupByWithCreator<K, V, C>(array: V[], groupFn: (V) => K, createCollectionFn: () => C, addCollectionFn: (C, V) => void): Map<K, C> {
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return array.reduce((map, value) => {
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const key = groupFn(value);
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let collection = map.get(key);
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if (!collection) {
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collection = createCollectionFn();
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map.set(key, collection);
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}
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addCollectionFn(collection, value);
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return map;
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}, new Map<K, C>());
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}
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export function countBy<V>(events: V[], mapper: (V) => string | number): { [key: string]: number } {
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return events.reduce((counts, event) => {
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const mappedValue = mapper(event);
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if (!counts[mappedValue]) {
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counts[mappedValue] = 1;
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} else {
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counts[mappedValue] += 1;
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}
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return counts;
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}, {});
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}
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export function tests() {
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return {
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countBy: assert => {
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const counts = countBy([{type: "foo"}, {type: "bar"}, {type: "foo"}], o => o.type);
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assert.equal(Object.keys(counts).length, 2);
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assert.equal(counts.foo, 2);
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assert.equal(counts.bar, 1);
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}
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}
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}
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