麻烦老师看一下，哪里有问题

来源：4-5 编程练习

KingBiao

2019-12-19 10:19:09

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>三种定义方式</title>
</head>
<body>
    <script type="text/javascript">
    // 在此处补充代码
    var calculate=function(){
        add:function(num1,num2){
            return num1+num2;
        }
        subtract:function(num1,num2){
            return num1-num2;
        }
        multiply:function(num1,num2){
            return num1*num2;
        }
        divide:function(num1,num2){
            return num1/num2;
        }
    }
    var result=calculate.add(calculate.subtract(21,22),calculate.multiply(24,5));
    document.write(result);
    </script>
</body>
</html>