Grab a notebook cell reference specified by a string

Is your feature request related to a problem? Please describe.

Observable is different: it functions like a spreadsheet, where cells (like formulas) run automatically whenever their referenced values change. Observable runs cells independently of their order in the notebook, giving you the flexibility to arrange your cells in whatever order you prefer for literate programming.

But it ain't a spreadsheet if you try to push the analogy further. In a spreadsheet, one can reference any cell whether it's explicitly named or not. Currently, Observable functions more or less the same as Airtable.

Sadly, there is currently no easy way to reference any notebook cell by string (or by using A1- & R1C1-style notation) as in Google Sheets or Excel… See Return a cell reference specified by a string and Return the reference specified by a text string.

PHP developers can also reference by string any available variable in global scope via $GLOBALS — whether it's good or bad practice is a matter of opinion…

It is currently undoable in Observable without resorting to hacks :-/

This is kind of strange considering there is this invaluable Minimap feature, which lists all the cells in a notebook and their dependencies. I understand you need to compartmentalize & secure things but I see no point in blocking a notebook from accessing its own cells programmatically ⁉️

Describe the solution you'd like

I'd like being able to reference a cell dynamically — whether it's explicitly named or not — within another notebook cell without having to modify this notebook cell snippet of code.

One could put the built-in JavaScript object Reflect to good use:

Reflect.ownkeys(ʘ) ; would return an array of all defined cells
Reflect.has(ʘ, 'foo') ; where foo is the name of a given notebook cell ; would return true if the specified cell is defined
Reflect.get(ʘ, 'foo') ; ibid. ; would return undefined if the specified cell is not defined
Reflect.get(ʘ, 2) ; where 2 references the second notebook cell in visual order ; would return undefined if the specified cell is not defined

… where ʘ (or __O__, or another aptonymic variable) would be a notebook property referencing all notebook cells.

Describe alternatives you've considered

For example, I was able to bend Observable to my needs using the following snippet:

viewof format = Inputs.radio(
  ((data) =>
    d3.group(
      Object.entries(data).map(([k, v]) => ({
        handle:
          0 === k.indexOf("json")
            ? k.toUpperCase()
            : "text" === k
            ? "plain " + k
            : k,
        data: Reflect.get(data, k)
      })),
      (d) => d.handle
    ))({ CSV: d3.csvFormat(rules), json, jsonl, text }),
  {
    label: "Format",
    key: "plain text"
  }
)

… where rules, json, jsonl, and text are notebook cell references.

This snippet grabs the content of the selected cell because all the referenced notebook cells do have names. It took me a while to figure how to achieve this ;-)

Additional context

Interestingly, you may examine defined notebook cells through Web Inspector > Page Resources > Extra Scripts:

"use strict";(
function(/* ...arguments? */){ return( /* ...cell content */ ) }
)
//# sourceURL=observablehq-\d+

"use strict";(
function(/* ...arguments? */){ /* ...cell statements */ }
)
//# sourceURL=observablehq-\d+

observablehq / feedback

Grab a notebook cell reference specified by a string #485