Question

In the JavaScript file, find the if statement that checks whether the date string has slashes. Note that it’s only checking whether there is one or more slash. Then, modify the code so it checks to make sure that the date entry has two slashes. If not, display the same error message as shown above. To do this, you need to store the result of the indexOf method and use it to first check whether a first slash was found and then use it as the starting point for trying to find a second slash.

Answer 1

Answer:

"use strict";

var $ = function(id) { return document.getElementById(id); };

var calculateDays = function() {  

   var event = $("event").value;

   var dt = $("date").value;  

   var message = $("message").firstChild;  

   var date, days, today, oneDay;

   // clear previous message

   message.nodeValue = " ";

   //make sure task and due date are entered and correct

   if (event.length === 0 || dt.length === 0) {

       message.nodeValue = "Please enter both a name and a date.";

   } else {

       //make sure due date string has slashes and a 4-digit year

       // if there is just 1 slash, then lastIndexOf should be

       // same as indeof

       if (dt.indexOf("/") === -1 || dt.indexOf("/") === dt.lastIndexOf("/")) {

           message.nodeValue = "Please enter the date in MM/DD/YYYY format.";

       }

       var year = dt.substring(dt.length - 4);

       if (isNaN(year)) {

           message.nodeValue = "Please enter the date in MM/DD/YYYY format.";

       }  

       //convert due date string to Date object and make sure date is valid

       date = new Date(dt);

       if (date === "Invalid Date") {

           message.nodeValue = "Please enter the date in MM/DD/YYYY format.";

       }

   }  

   // if no error messages, calculate and display days until event

   if (message.nodeValue === " ") {

       //calculate days

       today = new Date();

       oneDay = 24*60*60*1000; // hours * minutes * seconds * milliseconds    

       days = ( date.getTime() - today.getTime() ) / oneDay;

       days = Math.ceil(days);

       //create and display message

       if (days === 0) {

           message.nodeValue = "Hooray! Today is " + event + "!";

       }

       if (days < 0) {

           event = event.substring(0,1).toUpperCase() + event.substring(1); // capitalize event

           message.nodeValue = event + " happened " + Math.abs(days) + " day(s) ago.";    

       }

       if (days > 0) {

           message.nodeValue = days + " day(s) until " + event + "!";

       }

   }

};

window.onload = function() {

   $("countdown").onclick = calculateDays;

   $("event").focus();

};

Explanation: