jashkenas/underscore — pull request #1703 by megawac (2014-06-24 21:55:52+00:00)
Title: Avoid modifying arguments object

I'm not sure how you guys will feel about JIT optimizations but this can give a good boost to engine optimizers.

Relevant jsperf: http://jsperf.com/reduce-right-optimi/8

still some other places this pattern remains