Adding global validation before submit (javascript)

Context: need for validation or special javascript behaviour before POST.

Since the asp.net postback mecanism occurs with html POST method, it is possible to add an javascript event that replace the normal post event to force a special behaviour or validation.

This function define a pointer to the normal post event of the form, than it define a behaviour that will occur when the post event will fire. This behaviour decides if the form will really submit (ie firing a asp.net postback event).

// setting the handler of the main form:
SetSubmitHandler(document.forms[0]);

// handler definition to personalize
function SetSubmitHandler(form)
{
 // setting a pointer to the original submit function
 // to really post the form to the server
 form.orginalSubmit = form.submit;
 
 // function that replaces the normal post function
 form.newSubmit = function()
 {
  // special behaviour
  // .....  
  if (1==1)// validation goes here..
  {
  // validation is ok --> post to the server
   form.orginalSubmit();
  }    
 }
 // replacing the standard handler (posting to the server)
 // with the new handler
 form.submit = form.newSubmit;
}