Browser and system information. Uses FlashDetect (www.featureblend.com/javascript-flash-detection-library.html) and cookie.js (https://github.com/florian/cookie.js)

debounce.js

//     Underscore.js
//     http://underscorejs.org
//     (c) 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
//     Underscore may be freely distributed under the MIT license.
//
// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds. If `immediate` is passed, trigger the function on the
// leading edge, instead of the trailing.
function debounce(func, wait, immediate) {
  var timeout;
  return function() {
    var context = this, args = arguments;
    var later = function() {
      timeout = null;
      if (!immediate) func.apply(context, args);
    };
    var callNow = immediate && !timeout;
    clearTimeout(timeout);
    timeout = setTimeout(later, wait);
    if (callNow) func.apply(context, args);
  };
};

system_info.js

//= require cookie
//= require debounce
//= require flash_detect

var systemInfo = debounce(function() {
  var info = {};

  if (window.screen && window.screen.width && window.screen.height) {
    info["sr"] = window.screen.width + "x" + "" + window.screen.height;
  }

  if (document.documentElement
      && document.documentElement.clientWidth
      && document.documentElement.clientHeight) {
    info["vp"] = window.screen.width + "x" + "" + document.documentElement.clientHeight;
  }

  if (window.screen && window.screen.colorDepth) {
    info["sd"] = window.screen.colorDepth + "-bits";
  }

  var lang =  navigator.languages && navigator.languages[0] || // Chrome / Firefox
              navigator.language ||                            // All browsers
              navigator.userLanguage;                          // IE <= 10
  if (lang) {
    info["ul"] = lang;
  }

  try {
    info["je"] = navigator.javaEnabled();
  } catch (e) {
    info["je"] = false;
  }

  if (FlashDetect.installed) {
    info["fl"] =  FlashDetect.major + " " +
                  FlashDetect.minor + " " +
                  FlashDetect.revisionStr;
  }

  try {
    var protocol = (window.location.protocol || document.location.protocol);
    cookie.set(
      { sysinfo: JSON.stringify(info) },
      { secure: (protocol == "https:"), path: "/" }
    );
  } catch (e) {}
}, 250);

$(document).on("turbolinks:load", systemInfo)
$(window).on("resize", systemInfo)