Are you tired of writing the following?
Play it again Sam
That is pretty awesome if you ask me and since you are reading this I am assuming that you asked me. Below is a table containing the substitution strings, which I pulled directly from the console MDN docs. This works in the Chrome debugger in addition to Firebug.
|%d||Outputs an integer. Formatting is not yet supported.|
|%i||Outputs an integer. Formatting is not yet supported.|
|%s||Outputs a string.|
|%f||Outputs a floating-point value. Formatting is not yet supported.|
Disclaimer for trolls: Yes this could easily be hacked together. I am just bringing attention to the fact that it exists and you don't have to waste your time cutting the code yourself.