Alternative way of disabling the submit button?

You're on the right track. However, the way you have it written currently would enable the button and since buttons are generally enabled by default this probably would not do anything at all. You still need a way to disable the button when canSubmit() equals false.

A way to do this could be:

function enableSubmitEvent() {
  if (!canSubmit()) {
    $("#submit").prop("disabled", true);
  } else {
    $("#submit").prop("disabled", false);
  }
}

The way shown in the video is obviously the shorter way.

It is not a true alternative because you are only enabling the submit, but not disabling it. So if the user enters valid info into the form, submit is enabled. If they then change something and the form is no longer valid they can still submit it.

This is a working alternative:

function enableSubmitEvent() { 
  if (canSubmit()) { 
    $("#submit").prop("disabled", false); 
  } else  {
     $("#submit").prop("disabled", true); 
  }
}

There is more code here though, so I would say Andrew's code in the video is the slightly better way of doing it.