js 取 cookie

var mycookie = document.cookie;  
  		 var username='username';
		 var start1 = mycookie.indexOf(username+ "="); 
  		  if(start1!= -1){ 
 			 start=mycookie.indexOf("=",start1)+1;  
  			 var end = mycookie.indexOf(";",start); 
 		  if(end==-1){ 
  			end=mycookie.length;
			} 
 			var value=unescape(mycookie.substring(start,end)); 
		}