dagsheet
It's like a spreadsheet, but with explict representation of dependencies, and functions as data.
Live demo at https://mccalluc.github.io/dagsheet/.
To develop locally, you'll need to start an HTTP Server: AJAX will not allow the example files to be loaded with the "file://" protocol. You'll also want to be sure that you are not caching the files you're working on. Here's one approach:
$ npm install http-server -g
$ http-server -c-1