Redirect desktop site to mobile site using javascript.

redirect_to_mobile_site.html

/*If you have two different sites, one for mobile and another for desktop. When any user try to visit your desktop site
from mobile, then use below code on your desktop website in index.html or import this below code as external JS.*/

// Add below code in your head tag
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
<script>
    var isMobile = {
    Android: function() {
        return navigator.userAgent.match(/Android/i);
    },
    BlackBerry: function() {
        return navigator.userAgent.match(/BlackBerry/i);
    },
    iOS: function() {
        return navigator.userAgent.match(/iPhone|iPad|iPod/i);
    },
    Opera: function() {
        return navigator.userAgent.match(/Opera Mini/i);
    },
    Windows: function() {
        return navigator.userAgent.match(/IEMobile/i);
    },
    any: function() {
        return (isMobile.Android() || isMobile.BlackBerry() || isMobile.iOS() || isMobile.Opera() || isMobile.Windows());
    }
};
if( isMobile.any() ) 
{
//provide your mobile site
window.location.assign("http://www.yoursite.com/mobile/");
}
    </script>