Question

I want to run a code on every postback on client-side. Is there an event or something to do that?

Answer 1

If you just handle a form’s submit event, you won’t necessarily catch every __doPostBack(). A __doPostBack() that triggers an UpdatePanel refresh doesn’t submit the form, for example.

One way that you can make sure you know about every call to __doPostBack() is to redefine it:

var oldDoPostBack = __doPostBack;

function __doPostBack(eventTarget, eventArgs) {
  // Your code here, which will execute before __doPostBack,
  //  and could conditionally cancel it by returning false.

  oldDoPostBack(eventTarget, eventArgs);
}

Just be sure to do that near the end of the page or in a document.ready type event, so you can be sure __doPostBack is defined when you attempt this.