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-rw-r--r--browser/components/newtab/common/Dedupe.sys.mjs36
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diff --git a/browser/components/newtab/common/Dedupe.sys.mjs b/browser/components/newtab/common/Dedupe.sys.mjs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+export class Dedupe {
+ constructor(createKey) {
+ this.createKey = createKey || this.defaultCreateKey;
+ }
+
+ defaultCreateKey(item) {
+ return item;
+ }
+
+ /**
+ * Dedupe any number of grouped elements favoring those from earlier groups.
+ *
+ * @param {Array} groups Contains an arbitrary number of arrays of elements.
+ * @returns {Array} A matching array of each provided group deduped.
+ */
+ group(...groups) {
+ const globalKeys = new Set();
+ const result = [];
+ for (const values of groups) {
+ const valueMap = new Map();
+ for (const value of values) {
+ const key = this.createKey(value);
+ if (!globalKeys.has(key) && !valueMap.has(key)) {
+ valueMap.set(key, value);
+ }
+ }
+ result.push(valueMap);
+ valueMap.forEach((value, key) => globalKeys.add(key));
+ }
+ return result.map(m => Array.from(m.values()));
+ }
+}