To the folks downvoting, the following is from Facebook's Front End Tech Talk:
/**
* Adding a single line to this file requires great internal reflection
* and thought. You must ask yourself if your one line addition is so
* important, so critical to the success of the company, that it warrants
* a slowdown for every user on every page load. Adding a single letter
* here could cost thousands of man hours around the world.
*
* That is all.
*/