HOWTO: Make Marketo forms onValidate/onSubmit/onSuccess idempotent, like native DOM events (plus learn what “idempotent” means!)
Marketo’s onValidate and friends stack like DOM event listeners: they run in the order they were added. But there are still major differences:In Marketo, the listener stack isn’t deduped. If you add the same listener function 3 times, it’ll run 3 times. In contrast, DOM addEventListener(event,callback) checks if the callback was already added and if so, doesn’t add it again. In Marketo, all listeners always run. There’s no short-circuit method like stopImmediatePropagation(). In Marketo, to stop submission you call submittable(). There’s no event-level preventDefault(). (Note onValidate — but only onValidate — respects the callback’s return value, kind of like DOM inline event handlers.)Adding (1) is an easy tweak that makes it a lot easier to manage advanced form behaviors with lots of coordinated components. Adding (2) is quite tricky[1] and I’ll cover that another day. Might even throw in (3).😏 We’re adding idempotence to the Forms JS APIIdempotence is a show-offy CS term for an ac
