Error Parsing Javascript in Template

[scolby33]

I am trying to adapt wintersmith's default archive.jade template to Nunjucks and am having difficulty with this bit of javascript, which works correctly with the Jade template:

- var archives = _.chain(env.helpers.getArticles(contents)).groupBy(function(item) {
-    return item.date.getFullYear()
- }).value()

My attempt to implement this in Nunjucks looks like this:

{% set archives = _.chain(env.helpers.getArticles(contents)).groupBy(fucntion(item){return item.date.getFullYear()}).value() %}

When building or previewing, this raises a parseSignature error at column 82 of that line (after the 'm' of function(item)):

parseSignature: expected comma after expression

I have searched all over but cannot seem to find any mention of this issue or a solution. I find it hard to believe that this is a bug in either your plugin or in Nunjucks, but I don't know where else this issue could be coming from.