Check if exits an jquery script load

check-jquery

## One way

 if(!("jQuery" in window)) {
	
	    var head = document.getElementsByTagName('head')[0],
	    script = document.createElement('script');
	    script.type = 'text/javascript';
	    script.src = '/resources/js/lib/jquery-2.1.0.min.js';
	    head.appendChild(script);
	}

## Second way
if (typeof jQuery == 'undefined') {  

\\do somenthing if not exist
}
else
{
\\do somenthing
}