Building an efficient subscription for knockout computed observables

Subscribing to a ko.computed isn’t the same thing as subscribing to a ko.observable. Ryan Niemeyer has written on the topic and I’ll admit, it took me a while to wrap my head around it. I’ll go over the problem and how we bypass it, but the end result is really handy and reusable: a new ‘efficientlySubscribe’ method that is a part of all ko.computed’s.

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Extending Ryan Niemeyer’s protectedComputed

Ryan Niemeyer has a great article on the protectedComputed that he came up with, but I needed a little more functionality out of it. I ended up adding a few things and wanted to get it online for public consumption if anyone found the new functionality useful, so here it is!

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Changing an observableArray in 1 notification

I was just reading Ryan Niemeyer’s 2nd post about performance in knockout.js and I saw arrayPushAll. We ended up needing to use it for reasons other than performance, but performance does benefit greatly from its use.

We just had a problem (4/6/2012) where we were adding an array of items, one at a time in a loop, to an observable array. We wanted that notification of the array changing to trigger an ajax request, but we couldn’t because we were getting {n} notifications and we only wanted one request.

Initially I had to wire up the event in an odd way and that approach didn’t feel right since it seemed that we should be able to use the arrays changed notification. I should have thought to look up if ko had a slice or an equivalent, but I didn’t at the time. Now we just use arrayPushAll and this gives us a single notification because its a single change to the array. This is a much better solution and the added performance is great too!

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How to Use Knockouts Computed Observables with the Mapping Plugin

This is a blurb on using knockout‘s computed observables on a collection of items that are made observable via the mapping plugin. If you haven’t seen KnockoutJS then immediately go and watch all the demo / intro videos you can. You’ll be extremely impressed!

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