jecbot error 01

module.exports = (robot) ->
        robot.hear /突然の(.*)/i,(res) ->
                str = res.match[1]
                res.send "#{str}"
                len = str.length
                res.send len
                if len > 0
                        ans = ('人' for i in [0..len])
                        ans = ans.replace(/,/g, "")
                        res.send "#{ans}"

//////////////////////////////////////////////////////////////////////////

突然の死
jecbot> [Tue Nov 17 2015 10:42:12 GMT+0900 (JST)] DEBUG Message '突然の死' matched regex //突然の(.*)/i/
[Tue Nov 17 2015 10:42:12 GMT+0900 (JST)] DEBUG Executing listener callback for Message '突然の死'
死
1
[Tue Nov 17 2015 10:42:12 GMT+0900 (JST)] ERROR TypeError: Object 人,人 has no method 'replace'
  at TextListener.callback (/home/ec2-user/keita/jecbot/scripts/sudden.coffee:9:4, <js>:18:19)
  at executeListener (/home/ec2-user/keita/jecbot/node_modules/hubot/src/listener.coffee:65:11, <js>:53:19)
  at allDone (/home/ec2-user/keita/jecbot/node_modules/hubot/src/middleware.coffee:41:37, <js>:32:16)
  at /home/ec2-user/keita/jecbot/node_modules/hubot/node_modules/async/lib/async.js:274:13
  at Object.async.eachSeries (/home/ec2-user/keita/jecbot/node_modules/hubot/node_modules/async/lib/async.js:142:20)
  at Object.async.reduce (/home/ec2-user/keita/jecbot/node_modules/hubot/node_modules/async/lib/async.js:268:15)
  at /home/ec2-user/keita/jecbot/node_modules/hubot/src/middleware.coffee:46:7, <js>:35:22
  at process._tickCallback (node.js:442:13)


配列の中身を"人,人"にする事ができたのですが、そのまま表示するとカンマも一緒に出力されてしまうので
「str.replace」を使用してカンマを消そうと試みたのですが、エラーが。。。
もし上手いやり方があれば是非教えてくだされっ