Hi, I’m already on ES6’s 9th challenge, and its second time I encounter those three functions(filter(), map(), reduce()), did I missed some challenge? I searched but didn’t find about this.
The further along you go, the more you will be expected to do research when something is not familiar to you. This is possibly the most important skill that you need to gain in order to do more than follow tutorials, and FCC does less “hand holding” as you go on, so you can actually be prepared to do projects.
I haven’t used FCC in a loooong time but I remember the description of each challenge sometimes had some related links at the bottom. Maybe one of them mentioned a couple of links to MDN or something.
I think that external links were removed from the challenges because FCC doesn’t want external dependencies in their information.