Great explanation of how to read QR codes, thanks for the write up! Here's a nice one about 1D codes and how to decode your average UPC codes you find on products in (American) supermarkets:

https://scanbot.io/blog/how-do-barcodes-work/

Full disclosure: I work for Scanbot SDK, but we do offer PDF417 scanning for JS. It's a commercial solution that comes with a not-insignificant price tag, but it might be what you're looking for. You can check out the demo and documentation here: https://scanbot.io/trial/demo-web/barcode-demo/ , https://docs.scanbot.io/barcode-scanner-sdk/web/introduction...