Duplicating arrays of objects is well-trod territory as far as the engine goes. Your array isn't storing all the content, just a bunch of pointers to the old ob

Duplicating arrays of objects is well-trod territory as far as the engine goes. Your array isn't storing all the content, just a bunch of pointers to the old objects, so "a couple thousand" entries in the array is trivially small. Once you're dealing with millions you may consider using immutable.js, since that uses datastructures optimized on the assumption of immutability (eg less duplicating of whole arrays, more storing only the deltas). If you're using jira's web UI as an example, you'll find the overhead of array and object duplicating to be a tiny fraction of the cost for actually rendering all those items in browser. Probably in the one-billionth or less range of the total cost.