gistfile1.js

/* https://github.com/carhartl/jquery-cookie */

$("a.linkDownload").click(function(event) {
  .... other action on click of link
  $(this).bindDownloadEvents(event); // bind the form submit event
});

$.fn.bindDownloadEvents = function(event) {
  event.preventDefault();
  showDownloadIndicator(this);
  .... //Add the necessary form elements including json
  $("submit the form");
};

function showDownloadIndicator(link) {
  var timeCounter = 0; // used for keeping track of time elapsed, notify the user in case of delays

  disableLinkAndShowIndicator(link);  // disable the download link and start the "waiting" indicator

  // Start the setInterval to check for a cookie every 1 sec
  fileDownloadCheckTimer = window.setInterval(function () {
    timeCounter++;
    var cookieValue = $.cookie('fileDownloadStatus');
    if(timeCounter >= 20) { // timed out
      alert("Error", "We are experiencing issues with file download, please try again later.");
      finishDownloadAndRemoveIndicator(link);
    }
    else if (cookieValue == "complete") { 
      // server response has the cookie, do the cleanup and remove the cookie
      finishDownloadAndRemoveIndicator(link);
    }
   }, 1000);    
}

function finishDownloadAndRemoveIndicator(link) {
  $.cookie('fileDownloadStatus', null); // remove the cookie

  window.clearInterval(fileDownloadCheckTimer); // clear the setInterval

  removeIndicator(link); // remove the "waiting indicator"

  $(link).unbind("click").bind("click", function(e) { // bind the click event back to the link
    $(this).bindDownloadEvents(e);
  });
}

function disableLinkAndShowIndicator(link){
  showIndicator(link);
  $(link).unbind("click").bind("click", function(e) { e.preventDefault();});
}

function showIndicator(link) {
  ... code to show the indicator
}

function removeIndicator(link) {
    ... code to remove/hide the indicator
}