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


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

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


Technical background

The JavaScript functions 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