We've built in a console debugger into our Javascript SDK to help out during development.

To enable the console debugger you need to supply a second parameter when you setup and authenticate the SDK.

var myStore = new Commerce('pk_test_c57a31c6163575e6eebbe4ae4f33d8435d962f4f', true);

The console debugger only works when you are using a test api key, messages will not be shown if you are using a live API key.