Well the example given is bugged, as if you make updates at 0 and 50, then it never fires the function at 100 for the change that occurred at 50. If I didn't wa

Well the example given is bugged, as if you make updates at 0 and 50, then it never fires the function at 100 for the change that occurred at 50. If I didn't want to rely on the whole framework, I'd copy and paste the tested implementation (and dependencies) in underscore. Not that it's bad to know how to do it yourself, but I'd make sure my implementation was sound before sharing it as advice.