How to detect mobile userAgent in js

detectmob.js

function detectmob() {
             if (navigator.userAgent.match(/Android/i) ||
                 navigator.userAgent.match(/webOS/i) ||
                 navigator.userAgent.match(/iPhone/i) ||
                 navigator.userAgent.match(/iPad/i) ||
                 navigator.userAgent.match(/iPod/i) ||
                 navigator.userAgent.match(/BlackBerry/i) ||
                 navigator.userAgent.match(/Windows Phone/i)
             ) {
                 return true;
             } else {
                 return false;
             }
         }