Top 6 reasons why IE7 is complaining about your javascript

This blog post is now moved over here.

1. Source: Script tag is the first element of the page: The html page returned by the server contains “script” tag as the first element of the webpage. This problem occurs mostly in pages returned as a result of ajax call.

Solution: Introduce a fake div tag as the first element of the webpage. You can set the height of the div tag to zero so as to avoid any visual changes in your page. eg . < style=”height: 0px”>&nbsq;< /div > <script language=”javascript”>…..</script>

2. Source: Comma after the last element of an array: If you leave a comma after the last element of an array, it will raise an error in IE7 but not in firefox. For eg options = {‘item1′:’val1’, ‘item2′:’val2’,} will raise an error in IE7

Solution: It is obvious. Remove the damm comma.

3. Source:  Firebug console command: If you are using firebug “console” or any other command for debugging your javascript in Firefox and left these commands in your javascript, then IE7 will raise an error warning.

Solution: Again its obvious. Remove all the commands that are related to firebug javascript debugger.

4. Source: Trying to access non-existing identifier (id): if the javascript tries to access a non-existing element, it will break your javascript code in IE7.

Solution: Its difficult to identify this problem in IE7 as IE7 only reports the problem but not the element name that it is trying to find. However, it will give you a line number and character number as a part of the warning which can help in narrowing you search for the missing element.

5. Source: Defining variable without “var”:I was surprised to find this one. But within my document block for jquery, I defined a variable without “var” modifier and this raised an issue in IE7. Here is how my document block was originally coded

$(document).ready(function(){

library = “hello”;

message = “world”;

if(“form#” + library).submit(….

….

);

});

Solution: Use “var” modifier to define all you javascript variables. In the above case, after I added “var” modifier in-front of library and message variable, everything seemed to be working fine.

6: Source: <script /> tag : IE expects script tag to be XML compatible format. That is, it expects both starting (<script>) and ending <script/>) tag. Using shorthand for script tag, i.e, <script /> might create problems in IE. Thanks to Simon for reporting this problem.

Solution: Always use starting (<script>) and ending (</script>) tag.

Enjoy