jQuery $.ajax Method Ignored the Undefined Values

Recently, I used jQuery to get the data from the server client via $.ajax method. As we known that, we should send the request with some parameters. The code as follow.

$(document).ready(function(){
  $.ajax({
    url:'http://127.0.0.1/jq-undefined.php',
    data:{
      para1 : 1,
      para2 : 2,
      para3 : undefined
    },
    success:function(data){
      alert(data);
    },
  });  
});

According to Chrome DevTools, I get the result:

Yep, jQuery is smart, it can ignore the undefined values and avoid a lot of server errors. If you must send a undefined value, you can write like this

$(document).ready(function(){
  $.ajax({
    url:'http://127.0.0.1/jq-undefined.php?para3=undefined',
    data:{
      para1 : 1,
      para2 : 2
    },
    success:function(data){
      alert(data);
    },
  });  
});