when to use e.preventdefault code example

Example 1: js preventdefault

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

Example 2: preventdefault

e.preventDefault();

Example 3: js opposite of preventdefault

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

event.returnValue = true;

Example 4: e.preventDefault

event.preventDefault();