iPhoneVersion.js

function iPhoneVersion() {
  var iHeight = window.screen.height;
  var iWidth = window.screen.width;
  if (iWidth === 320 && iHeight === 480) {
    return "4";
  }
  else if (iWidth === 375 && iHeight === 667) {
    return "6";
  }
  else if (iWidth === 414 && iHeight === 736) {
    return "6+";
  }
  else if (iWidth === 320 && iHeight === 568) {
    return "5";
  }
  else if (iHeight <= 480) {
    return "2-3";
  }
  return 'none';
}

function isIphone() {
  return !!navigator.userAgent.match(/iPhone/i);
}

if ( isIphone() && iPhoneVersion() === "6"){
  //code..
}