dmajda/pegjs — pull request #150 by curvedmark (2013-01-10 08:50:01+00:00)
Title: Ignore `undefined` value for options object and `startRule` option

So calling parse like this will use the default options instead

var options = undefined
parser.parse(input, options)

And calling parser like this will use default `startRule` option instead

var options = {}
parser.parse(input, {startRule: options.startRule})