Cells
Double-click a cell, or press Enter on it, and type. Formulas start with = — try =A0+B0 or =(C1*2)/3. Every cell is a native <input> in one form, readonly until it is opened. A change reflects the cell's text onto its <td> and bumps the grid's revision; only formula cells re-derive their value, through one pure evaluator. That evaluator and the two-line reflection are the only app JS.
Task 7 of 7GUIs, a GUI programming benchmark.
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