Exception not working in javascript

Question

I have been reading through the W3Schools tutorials on JavaScript, and am having a hard time understanding why my script is not throwing an exception. I expect it to throw an exception on the call document.getElementById("paragraphs"), because there is no id that equals paraghraphs. Please let me know why it's not throwing an Exception?

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Design Patterns</title>
</head>

<body>  

<button type="button" onclick="throwException()">Click Me!</button> 
<p id="paragraph">I am a paragraph</p>

<script>

function throwException(){

try{            
        var errorContainer = document.getElementById("paragraphs").value;               
}catch(err){            
        errorContainer.innerHTML="An error occured...";
        }
}

</script>


</body>
</html>

I have been reading through the W3Schools tutorials -- that's your first mistake. :) — Barmar
– Barmar, Commented Nov 12, 2013 at 1:53
Try replacing throw "Hey I'm an exception!"; with throw new Error("Hey I'm an exception!");let me know if this helps... :) — Renato Gama
– Renato Gama, Commented Nov 12, 2013 at 1:53
There's no variable error in the catch block. Did you mean err? — Barmar
– Barmar, Commented Nov 12, 2013 at 1:55
I was starting to wonder if W3Shools was sufficient, seems like it leaves all the real details out :) — Jason
– Jason, Commented Nov 12, 2013 at 1:59
getElementById() doesn't throw an exception when it can't find the ID, it just returns null. — Barmar
– Barmar, Commented Nov 12, 2013 at 1:59

Ken Herbert · Accepted Answer · 2013-11-12 02:02:27Z

2

Your code isn't throwing an exception on var error = document.getElementById("paragraphs"); because document.getElementById() does not throw an exception when the element is not found, instead it returns null. Check this documentation under the "Notes" section.

Also, as indicated in a comment above, W3Schools is not a great resource. It is good for purely beginner activities to learn the very basics, but beyond that it is known to the wider community as a source of bad coding practices and sometimes just plain misinformation.

A much better documentation resource (it doesn't have tutorials, but has much better documentation, at least on Javascript) is the Mozilla Developer Network.

answered Nov 12, 2013 at 2:02

Ken Herbert

5,2465 gold badges31 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Exception not working in javascript

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related