javascript的一个找零的小程序

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script type="text/javascript">
        function check(){
            var sum=document.form.one.value;
            if(sum>100||sum<1){
                alert("请输入1~100之间的数！");
                return null;
            }
            var a=0,b=0,c=0,d=0,e=0;
            while(sum>=50){
                sum-=50;
                a++;
            }
            while(sum>=20){
                sum-=20;
                b++;
            }
            while(sum>=10){
                sum-=10;
                c++;
            }
            while(sum>=5){
                sum-=5;
                d++;
            }
            while(sum>=1){
                sum-=1;
                e++;
            }
            var str="应找零钱为：";
            var flag=0;
            if(a!=0){
                flag=1;
                str+="50元" + a + "张";
            }
            if(b!=0){
                if(flag){
                    str+="，";
                }
                flag=1;
                str+="20元" + b + "张";
            }
            if(c!=0){
                if(flag){
                    str+="，";
                }
                flag=1;
                str+="10元" + c + "张";
            }
            if(d!=0){
                if(flag){
                    str+="，";
                }
                flag=1;
                str+="5元" + d + "张";
            }
            if(e!=0){
                if(flag){
                    str+="，";
                }
                flag=1;
                str+="1元" + e + "张";
            }
            str+="。";
            alert(str);
        }
    </script>
</head>
<body>
    <form name="form">
        请输入找零的数量（数值在0~100之间）： <input name="one" type="text" >
        <input type="button" value="提交" onclick="check()">
   </form>
</body>
</html>