GetTagFromIdentifierAndTitle returning nulls - function PreSaveItem

Question

I'm attempting to add what should be a very straightforward date verification routine to a Sharepoint 2010 list.  It's documented all over the web, but for some reason, I can't get it to work.  The code is below:
<script language="javascript" type="text/javascript">
function PreSaveItem()
var date1 = getTagFromIdentifierAndTitle("input","DateTimeFieldDate","Start Date and Time");
var date2 = getTagFromIdentifierAndTitle("input","DateTimeFieldDate","End Date and Time");
var arrDate1 = date1.value.split("/");
var useDate1 = new Date(arrDate1[2], arrDate1[1]-1, arrDate1[0]);
var arrDate2 = date2.value.split("/");
var useDate2 = new Date(arrDate2[2], arrDate2[1]-1, arrDate2[0]);
if(useDate1 > useDate2)
alert("The End Date cannot happen earlier than the Start Date");
return false; // Cancel the item save process
return true; // OK to proceed with the save item
function getTagFromIdentifierAndTitle(tagName, identifier, title) 
   var len = identifier.length;
   var tags = document.getElementsByTagName(tagName);
   for (var i=0; i < tags.length; i++) 
      var tempString = tags[i].id;
      if (tags[i].title == title && (identifier == "" || tempString.indexOf(identifier) == tempString.length - len)) 
         return tags[i];
   return null;
}</script>
I've traced it via debug mode, and it hangs up when I'm trying to parse date1, which contains null values.  I can't understand why it's not pulling the date from the NewForm screen.
To answer the obvious question; yes, I have selected dates on the NewForm screen.
Any help or debugging tips would be greatly appreciated.

Answer 1

Hi,
The script works great in my environment, when start date is less than end date, a dialog will pop up for the warning message:
As you said, “it hangs up when I'm trying to parse date1”, I suggest you log out some information to the console of the browser to check that whether the “title” attribute
of the start date input control is “Start Date and Time” and whether the “date1” object holds the valid date value.
About Using the Console to view errors and debug in IE Developer Tools:
https://msdn.microsoft.com/en-us/library/ie/dn255006(v=vs.85).aspx
Thanks
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