When merging CSVs in the browser, handling mismatched columns and quoted cells changes everything. Here's how filetools does it.
Last week we shipped CSV merge/split/transpose tools for filetools, and the most interesting challenge wasn't CSV parsing - it was handling real-world data without a server. Here's how we handle the hard cases.
The Problem:
CSV files in the wild are messy. Columns don't always match. A cell value contains a comma and that comma is quoted. Headers are sometimes case-sensitive, sometimes not. When you build on a server, you can run a fast library and stream the result. In the browser, you have to make your merge operation deterministic from first load.
Our approach:
