跨域javascript心跳保持会话

var SM = SM || {};
SM.keepAlive = function () {
  var aliveUrl = "https://blog.maskalik.com/keep-me-alive.aspx",
    interval = 60 * 1000 * 10,
    that = {},
    alive = false,
    timer = {};

  that.isActive = function () {
    alive = true;
  };

  that.removeTrackingIframeIfPresent = function () {
    var frame = document.getElementById("keep-alive-iframe");
    if (frame) {
      document.body.removeChild(frame);
    }
  };
  that.sendKeepAlive = function () {
    if (alive) {
      that.removeTrackingIframeIfPresent();
      var frame = document.createElement("iframe");
      frame.setAttribute("src", aliveUrl);
      frame.setAttribute("id", "keep-alive-iframe");
      frame.setAttribute("style", "display:none");
      document.body.appendChild(frame);

      alive = false;
    }
  };

  that.start = function () {
    var allTextareas = $("textarea");
    allTextareas.live("keyup", that.isActive);

    var allLinks = $("a");
    allLinks.live("click mouseover", that.isActive);

    timer = setInterval(that.sendKeepAlive, interval);
  };

  return that;
};

var alive = SM.keepAlive();
alive.start();