[GitHub] [trafficcontrol] ocket8888 commented on a diff in pull request #7187: Minimize Snapshot diff for Server Server Capabilities

[GitBox <gi...@apache.org>]

ocket8888 commented on code in PR #7187:
URL: https://github.com/apache/trafficcontrol/pull/7187#discussion_r1026721927


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traffic_portal/app/src/common/service/utils/CollectionUtils.js:
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@@ -19,6 +19,39 @@
 
 var CollectionUtils = function() {
 
+	// minimizeArrayDiff reduces the size of an index-sensitive Array diff by
+	// making common elements in the old and new arrays have the same index.
+	this.minimizeArrayDiff = function (oldItems, newItems) {
+		const minimalDiffItems = [];
+		const addedItems = [];
+
+		let newItemsIndex, newItem;
+		const oldItemsIterator = oldItems.entries();
+		const newItemsIterator = newItems.entries();
+		for (let oldItemsNext = oldItemsIterator.next(), newItemsNext = newItemsIterator.next(); !(oldItemsNext.done || newItemsNext.done);) {
+			const [, oldItem] = oldItemsNext.value;
+			[newItemsIndex, newItem] = newItemsNext.value;
+			if (oldItem < newItem) {
+				newItemsIndex--;
+				minimalDiffItems.push(undefined);
+				oldItemsNext = oldItemsIterator.next();
+				continue;
+			} else if (oldItem > newItem) {
+				addedItems.push(newItem);
+				newItemsNext = newItemsIterator.next();
+				continue;
+			}
+			minimalDiffItems.push(newItem);
+			oldItemsNext = oldItemsIterator.next();
+			newItemsNext = newItemsIterator.next();
+		}
+		minimalDiffItems.push(...addedItems);

Review Comment:
   fyi, there's a builtin for just concatenating two arrays without doing a spread operation into a push: [`Array.prototype.concat`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat).



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