Question

If I dispatch a js event object (from a view), it is nullified by the time it gets to the event-handler. What gives?

  :on-click  (fn [event] (dispatch [:clicked event]))

Short Answer

If you want to dispatch a js event object to a re-frame event handler, you must call (.persist event) before the dispatch. React recycles events (using a pool), and re-frame event handlers run async. Find out more here

Longer Answer

It is better to extract the salient details from the event and dispatch them, rather than the entire js event object. When you dispatch pure, simple ClojureScript data (ie. rather than js objects) testing and debugging will be easier.

To put this point even more strongly again, think about it like this:

• a DOM on-click callback might tell us "a button was clicked"
• our application must then interpret that click. The click means the user wanted to achieve something. They had "intent".
• it is this "intent" which should be captured in the re-frame event which is dispatched. It is this intent which the event handler must later facilitate.

So, in summary, re-frame view functions should transform DOM events into re-frame events which capture user intent: "a button was clicked" becomes user wants to delete item with id 42

As a result, philosophically, low-level DOM objects have no place in an event.