Turn a CSV into a Markdown table, and back again

This is a small job that appears constantly once documentation lives in Markdown. A number comes out of a spreadsheet and needs to go into a README, a handover note, a proposal or a ticket, and it needs to arrive as a table rather than as a screenshot of one.

The reason to use something built for it rather than doing it by hand is the awkward characters. A pipe inside a cell ends the cell, so any value containing one breaks the whole table, and the value is usually something innocuous like a measurement or a path. The same goes for line breaks inside a quoted CSV field, which have no equivalent in a Markdown row at all and have to be turned into something else deliberately.

Alignment is the other thing that gets skipped. A table of numbers where the numbers are left aligned is harder to read than the same numbers aligned right, and Markdown supports the distinction with the colons in the separator row. Most quick conversions ignore it, which is why so many documented tables look approximately correct and read badly.

Going the other way is more useful than it first appears. A table that only exists inside a document is data nobody can work with. Pulling it back out to CSV means somebody can sort it, sum it, or check it against the system it was supposed to describe, which is often how a stale document gets found out.

It runs entirely in the browser, which for this applet is less about secrecy and more about not needing to think about it. A table on its way into a proposal may well contain client figures, and the correct amount of consideration to give a free web tool handling those is none, because it never sees them.

The wider point, if this is happening often: a table pasted into a document is a snapshot that starts going out of date immediately. That is fine for a proposal and a problem for anything that is meant to stay true. When the same table is being re-pasted every month, what is really needed is a report somebody can look at, not a document somebody has to maintain.