ariya/esprima — comment on commit 7443627e036ab6e018627ebfdf7087bf82f6bdc4
File: esprima.js line 180
By ariya:

slice does not work (in this context) for array (set for IE <= 7). Therefore the extra join(''). See also http://code.google.com/p/esprima/issues/detail?id=78#c17.