Underscore-prelude is a project mainly written in JavaScript, it's free.
A half-baked port of Haskell's standard Prelude module as an Underscore.js extension
A half-baked port of Haskell's Prelude as an extension to Underscore.js. I say half baked because I don't really want to port all of the datatypes over, but rather only the functions that can operate on Javascript's existing data types.