Actually, custom getters and setters exist in ES5: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects#Defining_getters_and_sett

Actually, custom getters and setters exist in ES5: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects#Defining_getters_and_setters https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guid... AmpersandJS, for example, implements its observable pattern in this way: http://ampersandjs.com/learn/state http://ampersandjs.com/learn/state That said, I don't think the pubsub/rx/observables pattern is the most optimal for UI development, since it still allows for cascading event chains. Modeling all application state as a large data structure that allows for efficient diffing — which nicely mirrors the diffing react does with both it's internal component tree and diffing with the DOM — is a much more straightforward approach. Just re-render your application 60 times a second, like a game engine, and make that process as efficient as possible.