jquery function return

function myFunction(p1, p2) {
  var a = "";
 $.post( "/url", function( data ) {a = data.result;});
  return a;
}function myFunction(p1, p2) {
  var a = "";
  $.ajax({
    method: "POST",
    url: "/url",
    data: {p1: p1,p2: p2},
    success: function (data) {a = data.result;},
    error: function (data) {a = data.result;}
    });
  return a;
}function add(a, b) {
  return a + b; //Return stops the execution of this function
}

var sum = add(5, 24); //The value that was returned got but inside the variable sum