窗添加功能时提示停止工作

var user = window.prompt("Welcome to the Vacation Planner. Please enter yourname");
document.getElementById("greeting").innerHTML += ", " + user;
var enterDays = document.getElementById("enterDays");
/*
function.calculateDays(){
    var dayMessage = document.getElementById("dayMessage");
    if(enterDays <4){
        dayMessage.innerHTML = "Short trips are always worth it!";
        }
    else if(enterDays<7){
        dayMessage.innerHTML = "Cool, you'll be there for a week"
        }
    else{
        dayMessage.innerHTML = "You'll have plenty of time to relax and have fun!"
        }
}*/
enterDays.onclick = calculateDays;

当我输入这个代码时,窗口。提示正确工作。但是当我取消对函数的注释时。calculateDays,窗口。提示停止工作。有人能解释为什么会发生这种情况以及如何解决它吗? 谢谢!!!