[atoav]

Don't panic! Do not despair! Solve it like any big problem: you split it into smaller, managable chunks and tackle them systematically, one by one.

For the syntax thing you might wanna pick out one particularily "bad" one and have your collegue explain it to you. Takes him maybe 15 mins and will safe you a good chunk of time. Where I work asking is expected. I ask our Network/Linix guru for things all the time. He asks me as well when I use something he does not know. Pretending to know everything won't get anybody ahead.

As for the regex hell: I always found tools that visualize the matches in realtime useful (like this: https://projects.verou.me/regexplained/). Just make sure the flavour of regex matches yours.

Edit: I suspect your collegue relies heavily on ES6 syntax (as I would). A overview of that can be found here: https://www.w3schools.com/Js/js_es6.asp

Make sure to give yourself a little time to play, e.g. try to replace something where you would use a for loop with an Array.forEach loop or something like that.

[casual-dev]

You are right, but me and my colleague are limited on time unfortunately, because there is so much work to do. I already asked him, if he could include me in his next project, just to watch, what he is doing from the boilerplate up. Maybe this clears out some of the question marks. And thank you for the resources. I already use regexr.com for visualisation, but this seems better for learning.