what does preventdefault do code example

Example 1: jquery preventdefault

$("a").click(function(event){
  event.preventDefault();
});

Example 2: js preventdefault

function(event) {
  event.preventDefault();
}

Example 3: js opposite of preventdefault

event.preventDefault(); //or event.returnValue = false;
//and its opposite(standard) :

event.returnValue = true;

Example 4: event preventdefault

event.preventDefault()

Example 5: javascript allow default

$('form').submit( function(ev){

         ev.preventDefault();

         //later you decide you want to submit
         $(this).unbind('submit').submit()

  });