Great interview question. Tons of nuance to drawing borders on adjacent cells, how to handle varying thickness, etc. Once you start looking closely, you notice the pixel differences between how this gets handled by various spreadsheeting tools.
Thanks for the report! This one's already on my list actually (selection negation & unique selection deduping) -- look for a fix soon.
One pivotal feature that is difficult to map onto 3P tools is our data table UI, which is a separate scrollable grid that floats on top of the main sheet. That, combined with the complexity of formula selection, inserting buttons into cells (header dropdowns, filter, sort), led us to decide that rolling our own solution for full control was the right choice.
I am the creator of DataGridXL (https://datagridxl.com), an Excel-like data grid component and it uses native scrolling. However, the document/sheet height/width is indeed limited by max div dimensions. Does your spreadsheet have a max?
I interviewed at a spreadsheet company (for a frontend role) and they asked, "how would you go about determining what cells need a border when a user clicks an individual cell, clicks a cell and selects multiple cells, clicks a cell next to an already selected cell." Fascinating problem and we talked about solutions for a little bit.
Noticed that you can't unselect a cell once it's selected? I'm on a Mac with Chrome (latest, no updates available).
Repo steps: 1. Select a few cells (⌘ + click) or an individual cell 2. Try unselecting (⌘ + click) those same cells clicked in #1 3. Cell is not unselected