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36 lines
1.1 KiB
JavaScript
36 lines
1.1 KiB
JavaScript
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/*
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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(array, groupFn) {
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return groupByWithCreator(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(array, groupFn, createCollectionFn, addCollectionFn) {
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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());
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}
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