Genius!

I know on this site we tend toward very minimal variable names

Do we tho? Why would we?

I know on this site we tend toward very minimal variable names, but ^this kind of descriptive naming is actually best practice

I like your take on this solution

Is this bad practice?

This is beautiful btw.

nice solution.

Just out of curiosity, why do you pass in Math as the value of this to apply?

var logparser = /(\d{4}-\d{2}-\d{2}\s+\d{2}:\d{2}:\d+,?\d+)\s+(ERROR|INFO|DEBUG)\s+\[(\w+):(\w+):?(\w+)?\]\s+(.+)/;
                                                  ^^^^^^^^

I could see something going wrong here, but the timestamp's not clearly specified.

var logparser = /(\d{4}-\d{2}-\d{2}\s+\d{2}:\d{2}:\d+,?\d+)\s+(ERROR|INFO|DEBUG)\s+\[(\w+):(\w+):?(\w+)?\]\s+(.+)/;
                                                                                                ^^^^^^^^

This could potentially lead to two invalid cases:

1. A colon without a trailing subfunction (will always happen)
2. A subfunction without a leading colon (won't happen here because the preceding (\w+) is greedy)

@schm0 Not sure what you mean - this is native JS, not Underscore.

This wouldn't work if it was passed an empty array, because an empty array isn't null.

The key variable needs to be declared, otherwise it'll throw an error in strict mode or be added as a property to the global object (window in the browser, global for Node).