How would I use a variable from JS as a percentile in ux?

Say I want to make a <Rectangle Width="x%" /> where x is a variable from a JS module. How would I go about this?

To clarify, this is the sort of thing I have tried:

  var Observable = require("FuseJS/Observable");
  var number = Observable(25);

  module.exports = {
      number: number
<Rectangle Width="{number}%" Height="100%" Fill="Blue" Alignment="Left" />

Right now you have to do the workaround mentioned here

There is also a proper fix for this coming in the release after the one we’re working on right now, as mentioned here

Great, thank you very much! This really helps!