Dirty Tricks for Dirty Problems

A while ago I needed the ability to display a "no image available" image in a list of products when an image for that product was not available on the server.

Normally, with access to a server side language, this would be easy to implement. In .NET it could be checked with a single line of code using the System.IO.File class and its static Exists method.

However, in my case, the path to the image was generated by a tool and I couldn't modify it. All I had access to was the client HTML for the image, but I always got back a full image path to the product's image, whether it existed or not. The code just assumed that there would always be an image available named after its product ID (e.g. 12345.jpg).

I could of course create "No image available" images for all the missing images, but that would have meant a lot of work. Besides, it wasn't future-proof as it was quite likely new products without images would pop up in the system.

Then I remembered a little client side trick using the onerror attribute. All I needed to do was change the src attribute of the image in its onerror handler, like this:

<img src="http://imar.spaanjaars.com/DoesNotExist.jpg"
   onerror="this.onerror=null; this.src='http://imar.spaanjaars.com/DoesExist.jpg';" /> 

When the image cannot be loaded successfully, the img element fires its onerror event. Inside the (in-line) handler for that event, a new image is loaded that does exist.

Simple, and easy to implement. Note that this solution may not work in all browsers, as it's currently not standards compliant. It looks like it's going to be added to HTML 5 though (warning: this is a huge document).


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On Tuesday, February 05, 2008 9:48:36 AM Sundeep said:
Hi Imar!.
I have been following this site from past 3 months. Its a great resource available on net. This technique is correct and would come handy when the image is stored in database too. When we try to retrieve data and bind to any data controls like datalist, gridview, etc, we would face the problem. To avoid it, this client side script works perfect.
Thanks,
Sundeep.
On Thursday, March 20, 2008 4:19:37 PM Juriaan said:
Hele nuttige tip. Moet je 'm zelf ook ff toepassen in je Planetwrox site bij Gig Pix :-)
On Thursday, March 20, 2008 6:25:54 PM Imar Spaanjaars said:
Ha Juriaan,

Dat zou op zich een goed idee zijn, ware het niet dat dat niet overeen komt met het boek. De "broken images" komen uit het hoofdstuk waar je leert om een photo album met pictures aan te maken, maar waar je nog geen plaatjes uploadt; dat komt later pas....  ;-)

Imar

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