List to Comma Separated

In short Converting a vertical list to a comma-separated line joins each entry with a comma, and doing it in reverse splits a comma-separated line back into a list. Both directions are needed constantly because spreadsheets, forms and code want the data in different shapes: a column copied from a spreadsheet arrives one item per line, while a tag field, a query parameter or a function argument wants it on one line. The quoting and trimming options are what make the result usable rather than nearly usable. Trimming removes the trailing spaces that a spreadsheet paste leaves behind, which otherwise appear before every comma. Quoting wraps each item, which is what SQL and JSON need. Two things to check. If any of your entries contains a comma of its own, a plain comma-separated line is now ambiguous and splitting it back gives the wrong answer — that is precisely the problem CSV quoting exists to solve, so quote in that case. And the space after each comma is a style choice: code usually wants it, a strict CSV usually does not.