I’m a big fan of Fiddler for a long time. Last week I had to test some jQuery compatibility issues with a new web application we were building. At first I was replacing all the Javascript files with newer versions, updating all the references and so on… Although this approach worked it was cumbersome and error-prone. Isn’t there a better alternative?
So how can you do this?
Remark: Don't forget to remove this rule afterwards.
Fiddler to the rescue!
I found the following post by Eric Law where he uses Fiddler to load a different version of jQuery without updating any reference:http://blogs.msdn.com/b/ieinternals/archive/2011/08/19/using-fiddler-to-verify-a-jquery-update-will-fix-a-compatibility-problem.aspx. Exactly where I was looking for!So how can you do this?
- First, download the (newer) version of the library you want to test.
- Start Fiddler and go to the AutoResponder tab. Use the Add… button to create a new rule to map requests for your Javascript library to the newly downloaded file.
- Also set the Unmatched requests passthrough option to ensure that Fiddler doesn’t automatically generate 404s for requests that don’t match any of the rules.
- Reload your web application you’ll see that Fiddler intercepts the request for the older library and returns the newer one instead.
Remark: Don't forget to remove this rule afterwards.