Pushing and Pulling: Three Reactivity Algorithms
Posted 6th March 2026 in Programming, Design-Patterns, ReactivityCover image based on Rain, Steam and Speed, J. M. W. Turner (1844) National GalleryContentsContentsIt’s looking like I’m going to need to build a reactive engine for work, so I’m going to prepare for that by writing down what I know about them. I want to look at three ways of building reactive engines: push reactivity, pull reactivity, and the hybrid push/pull combination that is used in a bunch of web frameworks.The Problem StatementThe simplest way to visualise reactivity, in my opinion, is as a spreadsheet. You have a series of input cells, containing your initial data, and a series of output cells containing the final results. In between are many more cells containing intermediate computations that need to be done…
