Concept for performance specific components

performance-check.js

// Parsed user agent
var userAgent = UAParser(navigator.useragent);

// Browser info
var browserName = userAgent.browser.name;
var browserVersion = userAgent.browser.major;

// OS info
var osName = userAgent.os.name;
var osVersion = userAgent.os.version;

// Check for low performance
var checkForLowPerformance = function() {
  var lowFeaturesDetected = !Modernizr.video;
  var lowOsDetected = (osName === "Android" && osVersion === "4.2.2");

  if (lowFeaturesDetected || lowOsDetected) {
    document.getElementsByClassName("low")[0].innerHTML = 'This thing is too slow!';
  } else {
    console.log('high performance');
  }
}

var showBrowserInfo = function() {
  document.getElementsByClassName("browsername")[0].innerHTML = browserName;
  document.getElementsByClassName("browserversion")[0].innerHTML = browserVersion;
  document.getElementsByClassName("osname")[0].innerHTML = osName;
  document.getElementsByClassName("osversion")[0].innerHTML = osVersion;
}

showBrowserInfo();
checkForLowPerformance();