CSV ⇄ JSON Converter

Both directions in one tool because they are one job in reverse — a spreadsheet export that a script needs to consume, or an API response a spreadsheet needs to open — and a form field's worth of switching between them beats keeping two tabs open.

Quoted fields are parsed properly

A regex split on comma is the usual shortcut for CSV, and it is wrong the moment a field contains one — an address, a note, a name with a suffix. Parsing here follows RFC 4180: a quoted field may contain commas and newlines, and "" inside a quoted field is an escaped quote, not the end of the field.

The CSV header is the union of every row's keys

Converting JSON → CSV, the header is built from every object in the array, not just the first one. A field only row 40 has still gets a column; rows without it get an empty cell rather than the field being silently dropped from the sheet.

Nested values become a JSON string in the cell

CSV has no representation for a nested object or array, so one is serialised into the cell as JSON text rather than flattened or dropped. It round-trips back through JSON.parse if you need the structure again; a spreadsheet will just show it as text.

A CSV row of name,age then Alice,30 converts to a one-object JSON array holding name and age, both as strings — CSV has no types, so a cell holding 30 is indistinguishable from a cell holding the text 30.