Simple snippet to disable submit buttons when submitting a form to prevent multiple submits. This is especially useful when the user is on a slow connection.

disablesubmit.js

(function (d) {
  var f = d.getElementsByTagName('form'),
      i = f.length;
  
  while (i--) {
    f[i].addEventListener('submit', function () {
      this.querySelector('[type="submit"]').disabled = 1;
    }, false);
  }
}(document));