AJAX Mailchimp signup form integration

Based on gbinflames' answer, I kept the POST and URL, so that the form would continue to work for those with JS off.

<form class="myform" action="http://XXXXXXXXXlist-manage2.com/subscribe/post" method="POST">
  <input type="hidden" name="u" value="XXXXXXXXXXXXXXXX">
  <input type="hidden" name="id" value="XXXXXXXXX">
  <input class="input" type="text" value="" name="MERGE1" placeholder="First Name" required>
  <input type="submit" value="Send" name="submit" id="mc-embedded-subscribe">
</form>

Then, using jQuery's .submit() changed the type, and URL to handle JSON repsonses.

$('.myform').submit(function(e) {
  var $this = $(this);
  $.ajax({
      type: "GET", // GET & url for json slightly different
      url: "http://XXXXXXXX.list-manage2.com/subscribe/post-json?c=?",
      data: $this.serialize(),
      dataType    : 'json',
      contentType: "application/json; charset=utf-8",
      error       : function(err) { alert("Could not connect to the registration server."); },
      success     : function(data) {
          if (data.result != "success") {
              // Something went wrong, parse data.msg string and display message
          } else {
              // It worked, so hide form and display thank-you message.
          }
      }
  });
  return false;
});

You don't need an API key, all you have to do is plop the standard mailchimp generated form into your code ( customize the look as needed ) and in the forms "action" attribute change post?u= to post-json?u= and then at the end of the forms action append &c=? to get around any cross domain issue. Also it's important to note that when you submit the form you must use GET rather than POST.

Your form tag will look something like this by default:

<form action="http://xxxxx.us#.list-manage1.com/subscribe/post?u=xxxxx&id=xxxx" method="post" ... >

change it to look something like this

<form action="http://xxxxx.us#.list-manage1.com/subscribe/post-json?u=xxxxx&id=xxxx&c=?" method="get" ... >

Mail Chimp will return a json object containing 2 values: 'result' - this will indicate if the request was successful or not ( I've only ever seen 2 values, "error" and "success" ) and 'msg' - a message describing the result.

I submit my forms with this bit of jQuery:

$(document).ready( function () {
    // I only have one form on the page but you can be more specific if need be.
    var $form = $('form');

    if ( $form.length > 0 ) {
        $('form input[type="submit"]').bind('click', function ( event ) {
            if ( event ) event.preventDefault();
            // validate_input() is a validation function I wrote, you'll have to substitute this with your own.
            if ( validate_input($form) ) { register($form); }
        });
    }
});

function register($form) {
    $.ajax({
        type: $form.attr('method'),
        url: $form.attr('action'),
        data: $form.serialize(),
        cache       : false,
        dataType    : 'json',
        contentType: "application/json; charset=utf-8",
        error       : function(err) { alert("Could not connect to the registration server. Please try again later."); },
        success     : function(data) {
            if (data.result != "success") {
                // Something went wrong, do something to notify the user. maybe alert(data.msg);
            } else {
                // It worked, carry on...
            }
        }
    });
}