get the url parameter of the current page

function getUrlParams(name) {
  var reg = new RegExp('(^|&)' + name + '=([^&]*)(&|$)', 'i');
  var r = window.location.search.substr(1).match(reg);
  if (r !== null) {
    return decodeURIComponent(r[2]);
  }
  return null;
}