Try this:
For detecting touch devices(including touchscreen monitor)
var is_touch_device = 'ontouchstart' in document.documentElement;
if(is_touch_device){
//code for touch devices
}
for only detecting mobile devices:
if( /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ) {
//code for touch devices
}