判断是否为数字的代码出错，错那儿了？

Question

 function isNumber(num){                    if( !isNaN(num.value) && (num.value != "")){                        return true;                     } else {                        return false;                     }isNumber(5) 返回false 不知道那里错了

Answer 1

function isNumber(num){return typeof(num)==="number"
                    }