This indicates that a JavaScript function couldn't be found. Most likely, a custom checkout is being used and not all JavaScript files from our module or from Magento itself are loaded properly.


To resolve this, make sure that the following files are loaded correctly:

  • all JavaScript files from our module, and
  • the default JavaScripts for the Magento checkout.


Technical background

The JavaScript functions of our modules are usually called like this:

object.function()

If a function is not found in the given object, it results in the above TypeError. For more detailled information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_function