I encountered a small issue on javascript while doing a small hack for a VBulletin plugin. Sometimes a javascript function was included, sometimes not.
So I needed a way to check if that function was or wasn’t defined so I can call it safely (without any error message). In case you ever need something like this .. here is the code 
JAVASCRIPT
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if(typeof functionNameToCheck == ‘function’) {
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//you can now safely call your function
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}
Cool, Your rock.
Nice trick.