js制作计算器

<script type="text/javascript">
            var number1 = parseFloat(prompt("请输入第一个数值"));
            var fh = prompt("请输入符号");
            var number2 = parseFloat(prompt("请输入第二个数值"));
            var result;
            if(fh == "+") {
                result = number1 + number2;
            } else if(fh == "-") {
                result = number1 - number2;
            } else if(fh == "*") {
                result = number1 * number2;
            } else if(fh == "/") {
                result = number1 / number2;
            } else if(fh == "%") {
                result = number1 % number2;
            } else {
                result = "请输入正确的";
            }
            alert(result)
    </script>