A variable eCommerce API is available to use during the e-commerce flow. As part of this API, there is a listener that can register (stepChanged) to monitor for changes in steps during the process flow. When a step changes, this listener is called, and is passed 2 variables: the step number the user is coming from and the step number they are going to. Step numbers are 0-index based.

getSteps()

<script>

     eCommerceAPI.stepChanged(  function(fromStep, toStep) { 
          console.log("Changed from step " + fromStep + " to " + toStep);
     }

</script>