This is a simplistic spreadsheet I used to teach myself the basics of React (and a bit of Ramda) and how it works within Meteor. It uses,eval so there are security issues that would need to be addressed before it could be used for anything real. The advantage of using eval, though, is that you get all the functionality of JavaScript for free.
Every cell is evaluated as a Javacript expression, and if that expression returns a function, that function gets called. If a cell does not evaluate as valid JS, it's printed as-is in the cell - a simple way to add text cells without adding cell types. cell(col, row) is provided to refer to the output of other cells, which are numbered both for rows and columns (starting with zero – this is JavaScript!). So cell(0, 0) is like A1 in Excel, and cell (1, 3) is B4.
Cell reactivity is provided with Tracker and Minimongo. It already has a few optimizations to reduce unnecessary recalculations: Cell formula results are cached, and cells also save an isNotReactive property to cache the reactivity status (why calculate "Total" or 8?).
It uses a sparse data model that renders blank cells as needed using some functional code.
There are many, if this were to turn into anything real. A few of note:
- Add users/remove insecure
- Allow multiple sheets
- Add a real selection function, with the ability to select multiple cells (right now, click toggles formula/result)
- Allow cell types (now, all are JS – text is just anything that throws an error when
evaled) - Render more interesting cell contents. What if you could have web content (say a D3 chart or a youtube video) as a cell?
- Add any of an infinite number of additional features a real speadsheet would have.