Suppose you want to assign an event handler function to an click event of any element
$(document).on('click', '.disable-user', disableUserConfirmation());
when you run the app the function
disableUserConfirmation() gets executed any way, however the event handler function expected to run when the event is triggered wont work. You can see the error in the console.
Uncaught TypeError: undefined is not a function
What happens in callbacks is, when the jQuery’s function ‘on’ want to execute the function object it just appends the parenthesis after the function name and executes it.