IE9 problems with document.GetElementById()

I have worked in the past for corporate clients who are still using IE9. So despite IE and IE9 in particular not being that widespread in the wild, for these intranet systems, my apps must support IE9.

This is not usually a problem, but I do recall a problem occurring in the past which went against what you might expect.

I had some JavaScript whose job it was to open a popup on a web page and pass some data from the page to the popup so the user could review it and press “Search”. When the data was found, the user pressed a “Select” link on the popup and the JavaScript passed the data back to the original page and closed the popup. Should be simple right?

The JavaScript code that transferred the data looked something like this:


var custRegCodeTextBox = document.getElementById('CustRegCodeTextBox');
var destCustRegCodeTextBox = document.getElementById('DestCustRegCodeTextBox');
destCustRegCodeTextBox.value = custRegCodeTextBox.value;
$('#popup').fadeIn(700);


The code worked absolutely fine on my Windows 7 development machine running the same version of IE9 as the client (9.0.8112.16421 – 9.0.35) but it failed with JavaScript errors on the client. Why did this occur? A lot of head scratching and trial and error ensued because isn’t document.getElementById one of the most fundamental things?

The solution was to change the code to use jQuery throughout, e.g.:


var custRegCodeTextBox = $('#CustRegCodeTextBox');
var destCustRegCodeTextBox = $('#DestCustRegCodeTextBox');
destCustRegCodeTextBox.val(custRegCodeTextBox.val());
$('#popup').fadeIn(700);


Why did this work? The best I have to offer are two reasons:

1. ASP.NET Webforms will generate id=”Something” name=”Somethingelse” even when ClientIDMode=”Static”. This may have been something to do with it.
2. The customer had intranet compatibility mode turned on, and nothing I could do in the page would turn it off.

Anyway, its not very often that using a library solves a problem, usually the opposite is true, if the library introduces a bug, going to the building blocks normally solves it. This just shows to me just how good jQuery really is.