Aurelia Command (Promise Binding) is a gist I felt I needed to post as it took several missteps to complete, a lot of back and forth with Aurelia’s documentation, and an unhealthy dose of frustration for something I thought should be easy to do in Aurelia and possibly should be easy to find an existing working example. Hopefully this gist and the below write-up may come in handy to others looking for similar functionality.

What I Was Looking For

I wanted a way to systematically intercept any click.trigger binding on a button that returned a promise and add a modicum of progress reporting (disable the button, Toastr notifications, maybe a spinner like NProgress).

What I Built

The gist is an Aurelia Custom Attribute that can be used in place of click.trigger, once it has been required into your view:

Lessons Learnt

These things in particular took a surprising while to find flipping back and forth between Aurelia’s documentation pages and source code.


The bindingContext passed to a Component’s bind(bindingContext, ...) is the VM object. In one mostly finished version I was still using command.bind and trying to Function.bind() the function being bound to the attribute’s value and bindingContext was what I needed for that, but I hadn’t realized what bindingContext was, it’s name and the documentation didn’t quite make it clear. (Enter painful breakpoint inspections and console.log debugging.)

Call Data Binding

This was the big piece I needed that lead to the search for something like bindingContext in the first place, which I finally discovered in Aurelia’s Cheat Sheet while looking for something unrelated later in the day. .call is the magic binding syntax supported by .trigger and .delegate, but available to custom attributes. I understand why these things have different names, but it makes discoverability tough and makes me wonder if there might have been a way to better unify some of the . binding actions in Aurelia.

Aurelia Cheat Sheet

The most complete Aurelia documentation still seems to be the Cheat Sheet. I guess the lesson is check and re-check the Cheat Sheet. Hopefully the rest of Aurelia’s documentation might eventually catch up. Especially there seems to be need of a good Data Binding focused document (especially for those coming from Durandal because Knockout had pretty strong documentation on its data binding engine).

Get The Gist