I want to debounce a stream – but only if the source value is the same as before. How would I do this with RxJS 5?
I do not want to emit a value if the value is the same and I emitted it previously within a specified time window. I should be able to use the value from the stream – or compare function similar to distinctUntilChanged.
This rxjs6+ operator will emit when the source ‘value’ has changed or when some ‘delay’ time has passed since last emit (even if ‘value’ has not changed):
It depends on what you’re trying to do; I came upon this question when I was trying to do something similar, basically debouncing but with different debounces for different values of an object.
After trying the solution from jayphelps I couldn’t get it to behave as I wanted. After much back and forth, turns out there is an in built easy way to do it: groupby.
Output:
Jsbin: http://jsbin.com/savahivege/edit?js,console
This code will group by the bid ID and debounce on that, so therefore only send the last values for each.
update for rxjs 6 :
I’m not aware of any way to do this with without creating your own operator because you need to maintain some sort of state (the last seen value).
One way looks something like this:
Now that you see an implementation you may (or may not) find it differs from your expectations. Your description actually left out certain details, like if it should only be the last value you keep during the debounce time frame or if it’s a set–basically
distinctUntilChanged
vs.distinct
. I assumed the later.Either way hopefully this gives you a starting point and reveals how easy it is to create custom operators. The built in operators definitely do not provide solutions for everything as-is, so any sufficiently advanced app will need to make their own (or do the imperative stuff inline without abstracting it, which is fine too).
You can then use this operator by putting it on the Observable prototype:
Or by using
let
:If you can, I recommend truly understanding what my code does, so that in the future you are able to easily make your own solutions.
Here is my RXJS 6+ version in typescript that works 100% as originally requested. Debounce (restart timer) on every new source value. Emit value only if the new value is different from the previous value or the debounce time has expired.
Providing an answer for RxJS 6+ with the method suggested by @samberic in an
ngrx
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