Catching "NullPointerExceptions" in JavaScript

Posted by Lenni on Stack Overflow See other posts from Stack Overflow or by Lenni
Published on 2010-04-27T12:31:14Z Indexed on 2010/04/27 12:33 UTC
Read the original article Hit count: 236

Filed under:

JavaScript

|

error-handling

I'm writing quite a bit of code in Prototype.js which returns null if a DOM-id wasn't found.

$("someId").show();

If someId doesn't exist, a method will be called on null, which halts the entire program, in effect disabling all JS effects after the error. I could just check for null before executing such a statement, but this is getting tiring.

I would like to catch an exception but I'm not sure which one its is. MDC lists the following ECMA Script error types:

* Error
* EvalError
* RangeError
* ReferenceError
* SyntaxError
* TypeError
* URIError
* DOMException
* EventException
* RangeException

Also, do browsers have a unified way of dealing with a method call on null?

© Stack Overflow or respective owner

Related posts about JavaScript

CHAT ROOMs 7 by 6

as seen on Stack Overflow - Search for 'Stack Overflow'
I am looking for chatroom on one page with 7 loggedin users and 6+rows for say 42 users.these users will keep on adding wthnew users.Need urgent help.A PRETTY UNUSUAL Q FOR MOST OF U.What is MORE REQ new features: Usernames are unique to users currently chatting You can see a "currently chatting"… >>> More
Integrating JavaScript Unit Tests with Visual Studio

as seen on Stephen Walter - Search for 'Stephen Walter'
Modern ASP.NET web applications take full advantage of client-side JavaScript to provide better interactivity and responsiveness. If you are building an ASP.NET application in the right way, you quickly end up with lots and lots of JavaScript code. When writing server code, you should be writing… >>> More
Has Javascript developed beyond what it was originally designed to do?

as seen on Programmers - Search for 'Programmers'
I've been talking with a friend about the purpose of Javascript, when and how it should be used, etc. He quoted that: JavaScript was designed to add interactivity to HTML pages [...] JavaScript gives HTML designers a programming tool HTML authors are normally not programmers… >>> More
PHP, javascript, single quote problems with IE when passing variable from ajax post to javascript fu

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi! I have been trying to get this to work for a while, and I suspect there's an easy solution that I just can't find. My head feels like jelly and I would really appreciate any help. My main page.php makes a .post() to backend.php and fetches a list of cities which it echoes in the form of: <li… >>> More
Javascript in XSL that is loaded by Javascript

as seen on Stack Overflow - Search for 'Stack Overflow'
Is there anyway to have javascript run when a XSL sheet has been applied to an XML file by Javascript? I am using a JQuery plugin to apply the sheet to the xml but the javascript that is located inside of the XSL file will not run. I put the Javascript at the bottom of the file and it still does… >>> More

Related posts about error-handling

Good SQL error handling in Strored Procedure

as seen on Developer IT - Search for 'Developer IT'
When writing SQL procedures, it is really important to handle errors cautiously. Having that in mind will probably save your efforts, time and money. I have been working with MS-SQL 2000 and MS-SQL 2005 (I have not got the opportunity to work with MS-SQL 2008 yet) for many years now and I want to… >>> More
Error Handling Examples(C#)

as seen on DotNetBlocks - Search for 'DotNetBlocks'
“The purpose of reviewing the Error Handling code is to assure that the application fails safely under all possible error conditions, expected and unexpected. No sensitive information is presented to the user when an error occurs.” (OWASP, 2011) No Error Handling The absence of error… >>> More
Building an Error-Handling Mechanism

as seen on Internet.com - Search for 'Internet.com'
Are errors chasing away your visitors? Let Marc Plotz show you how to handle them effectively. ... >>> More
Building an Error-Handling Mechanism

as seen on Internet.com - Search for 'Internet.com'
Are errors chasing away your visitors? Let Marc Plotz show you how to handle them effectively. ... >>> More
Improving ANTLR DSL parse-error messages

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm working on a domain-specific language (DSL) for non-programmers. Non-programmers make a lot of grammar mistakes: they misspell keywords, they don't close parentheses, they don't terminate blocks, etc. I'm using ANTLR to generate my parser; it provides a nifty mechanism for handling RecognitionExceptions… >>> More