I can't copy the generated link directly (without ctrl+C)
I am usign document.execCommand('copy') but it seems it has no effect.
If code has no AJAX then its working pefectly.
Here's the 
HTML:
<div class="permalink-control"> </div>
JQUERY:
    $(".permalink-control")
          .append(
            '<div class="input-group">' +
            '    <span class="input-group-btn"><button type="button" class="btn btn-default" title="Get Permalink"><span class="glyphicon glyphicon-link"></span></button></span>' +
            '    <input type="text" class="form-control">' +
            '</div>'
          );
        $(".permalink-control input")
          .hide()
          .focus(function () {
            // Workaround for broken selection: https://stackoverflow.com/questions/5797539
            var $this = $(this);
            $this.select()
              .mouseup(function () {
                $this.unbind("mouseup");
                return false;
              });
          });
        $(".permalink-control button")
          .click(function () {
            var $this = $(this);
            $.ajax({
              url: "https://api-ssl.bitly.com/shorten",
              dataType: "jsonp",
              data: {
                longUrl: window.location.href,
                access_token: "your access token",
                format: "json"
              },
              success: function (response) {
                var longUrl = Object.keys(response.results)[0];
                var shortUrl = response.results[longUrl].shortUrl;
                if (shortUrl.indexOf(":") === 4) {
                  shortUrl = "https" + shortUrl.substring(4);
                }
                $this.parents(".permalink-control")
                  .find("input")
                  .show()
                  .val(shortUrl)
                  .focus();
              },
              async:false
            });
          });
UPDATE:
How do I copy to the clipboard in JavaScript?
is not answer to my question as My code also copies without using ctrl+C if AJAX is not there.
However when I am using AJAX document.execCommand('copy') is not working.
 
     
    