einars/js-beautify — comment on commit a6dd2d51a2bdd10bbcd42ef368d5ab3367a66e64
File:  line 0
By Infocatcher:

var comment_mark = '<-' + '-';

Why not "<!--"?

trimmed.substring(0, 4) === comment_mark

And here 4 and not 3 for '<-' + '-' :)