One of the mistakes I see a lot of beginners make is fretting over remembering EVERY detail of EVERY function or syntax or method they use. This is really true of functions and parameters regardless what language you are using.
Instead focus on the techniques and that the functions/methods/objects/classes EXIST, then if you use them double-check your memory against the manual. PHP is a stunning example of this where php.net is a GREAT manual that's easily searched, is crossed reference, and filled with practical examples of not just usage, but in many cases WHERE something would be most useful.
Were that the official ECMAScript documentation was as well written and organized... or HTML... or CSS. I swear everything the W3C does is like it's written in Finnish, translated to Japanese by a Russian, then Google Translated to English. There's a reason nubes and rubes get duped into the halfwit bull that is W3Schools and people in the know go to MDN.
Use a function, use a class, use an operator you don't use very often, RTFM again. AS YOU ARE DOING IT!
It's part of why I advocate that beginners and experts alike should TRY to set up a multiple display system, that way you can keep a browser window to an online manual or PDF open on one display whilst coding on the other. Personally, I'm a three display kind of guy.