Message from JavaScript discussions

November 2017

— This way, for each iteration, you have access to current and previous version of an "entry"


.once may be slow
useOldEntry HAS to be called synchronously within the callback to avoid possibility of skipping entries

— Pros:
Pure functional ish
Gets the job done

— Alright maybe I need to see this in action in my actual code to see the picture

— But, ehh, monads may be nicer

— Because, yes the concept seems doable

— But I can't see the spot to fit It

— I have an actual nodejs example

— A HTTP server that increments a counter without modifying state


function count(i) {
server.once('request', function (req, res) {
return count(i + 1);


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— Use on existing server to create a request counter

— The "pro" here is that it avoids mutating state
The con is that this STILL isn't a pure functional monadic interface

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