How to apply a function to all selected cells

JupyterLab extensions
1

I’m trying to write an extension that needs to apply some stuff on all the selected cells (or the active cell if no multiple selection is done)

As a first attempt I have written this,

export const apply_on_cells = (
  notebookTracker: INotebookTracker,
  scope: Scope,
  to_apply: (cell: Cell) => void,
) => {
      const { anchor, head } = notebook.getContiguousSelection()
      // when only one cell is selected/active, both are null
      if (anchor === null || head === null) {
        actionCells = [activeCell]
      } else {
        actionCells = notebook.widgets.slice(anchor, head + 1)
      }
      // console.log(`apply_on_cells with scope=${scope} on ${actionCells.length} cells`)
      actionCells.forEach(to_apply)
}

but it does not always work, and in some cases I get this error

image
image1344×146 32.8 KB

How should I write the code to iterate over all the selected cells ?

(there seems to be an underlying assumption that the active cell is always the first of the selected cells; but there are very common moves that break this assumption: use Command-A to select all cells; or use shift-down arrow to select more cells going down, etc…)

thanks !