function checkone(){
            clearall();
            var hobby = document.getElementsByName("hobby");
            var j=document.getElementById("wb").value;
            for(var i=0;i<j.length;i++){
                if(j.charAt(i)>6 || j.charAt(i)<1){
                    alert("越界,请重新输入！");
                    document.getElementById("wb").value="";
                }
            }
                for(var n=0;n<j.length;n++){
                   
                        hobby[(j.charAt(n))-1].checked=true;
                }

            
            
        }

这段不明白，拜托大神指点,charAt