Is there any library that does have the diffing feature you're talking about? It sounds like you're describing something like two-way binding, where some code i

Is there any library that does have the diffing feature you're talking about? It sounds like you're describing something like two-way binding, where some code is listening to a callback that fires whenever (for example) an item gets added to an array. I don't know about every JS UI library, but React certainly doesn't work this way. React would indeed just see that the array object has changed and would go through every element inside. That doesn't seem to be a performance problem, even with thousands of items, although you'll probably want some pagination if your app would otherwise need to generate or change thousands of DOM elements.