Can I stop a post back by using javascripts confirm?

Question

I have an aspx page with a asp.net button on the page:

Answer 1

You have to return the value from the function in the event handler:

OnClientClick="return ConfirmDelete();"

By the way, you don't need all that logic in the function, just return the result from the confirm call:

function ConfirmDelete() {
  return confirm("Are you SURE you want to delete this item?");
};