Jquery function BEFORE form submission

You can use the onsubmit function.

If you return false the form won't get submitted. Read up about it here.

$('#myform').submit(function() {
  // your code here
});

$('#myform').submit(function() {
  // your code here
})

The above is NOT working in Firefox. The form will just simply submit without running your code first. Also, similar issues are mentioned elsewhere... such as this question. The workaround will be

$('#myform').submit(function(event) {

 event.preventDefault(); //this will prevent the default submit

  // your code here (But not asynchronous code such as Ajax because it does not wait for a response and move to the next line.)
  
 $(this).unbind('submit').submit(); // continue the submit unbind preventDefault
})