Check IsMobile in javascript

<script>
  var isMobile = false;
  if (navigator.userAgent !== undefined) {
      var userAgent = navigator.userAgent.toLowerCase();
      var iPhoneIndex = userAgent.indexOf("iphone");
      var iPadIndex = userAgent.indexOf("ipad");
      var isIPhone = (iPhoneIndex !== -1 && iPadIndex === -1) || (iPhoneIndex !== -1 && iPhoneIndex < iPadIndex);
      var isAndroid = userAgent.indexOf("android") !== -1 && userAgent.indexOf("mobile") !== -1;
      var isOtherMobile = userAgent.match(/^.*?(ipod|blackberry|mini|windows\\sce|palm|phone|mobile|smartphone|iemobile).*?$/) != null;
      isMobile = isIPhone || isAndroid || isOtherMobile;
  }
</script>