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function addJavascript(jsname) {
	var th = document.getElementsByTagName('head')[0];
	var s = document.createElement('script');
	s.setAttribute('type','text/javascript');
	s.setAttribute('src',jsname);
	th.appendChild(s);
}

if (screen.width > 500)
{
    addJavascript("your_domain/js/jquery_computer.js");
}
else
{
    addJavascript("your_domain/js/mobile_version.js");
}