Ajax表单发送错误

I'm have a form that sends data to a server. When the form is usual HTML it works fine. All data is sent to the server without error. However when I change the form to use AJAX I get an error.

<form id="form" action="handler.php" method="POST"> <!-- it's work -->
    <input id="contact_name" type="text" name="name" placeholder="NAME">
    <input id="contact_phone" type="text" name="phone" placeholder="PHONE">
    <button type="submit">Get call</button>
</form>

$(document).ready(function() {
    /*this does not work*/
    $('#form').on('submit', function(e) {
        var dataf = $(this).serialize();
        $.ajax({
            url: 'handler.php',
            type: 'POST',
            data: dataf,
            success: function(response) {
                console.log(JSON.stringify(response));
            },
            error: function(response) {
                console.log(JSON.stringify(response));
            }
        });
    });
});

In console I get this:

{"readyState":0,"responseText":"","status":0,"statusText":"error"} 

You have to add e.preventDefault();

$(document).ready(function(){/*this does not work*/
  $('#form').on('submit', function(e) {
    e.preventDefault();
    var dataf = $(this).serialize();
      $.ajax({
        url: 'handler.php',
        type: 'POST',
        data: dataf,
        success: function(response) {
          console.log(JSON.stringify(response));
        },
        error: function(response) {
          console.log(JSON.stringify(response));
        }
      });
  });
});

<button type="submit">Get call</button>

should be

<button type="button">Get call</button>

Since you are submitting it manually via jQuery.