What 10 Things Should a Serious Javascript Developer Know Right Now?

Scope:

If you don't understand this intimately then you aren't that serious about this language. This is the number one point intentionally and I cannot stress it enough.

Architecture

You don't have to be a master software architect, but if you cannot perform some basic planning and put pieces together without massive layers of tooling you are an imposter. Expecting frameworks and other tools to simply do it for you isn't very impressive.

DOM

It is very common to see developers hiding from the DOM by layers of abstractions and other stupid crap. querySelectors are great, but are also 2800x slower than the standard DOM methods. That isn't trivial. These methods are super simple, so there is no valid excuse for developers fumbling over this or hiding in fear. http://prettydiff.com/guide/unrelated_dom.xhtml

Node.js

If you are a serious developer should have a pretty solid grasp of how to walk the file system. You should understand how to conveniently read files as text or less conveniently read files as bit for bit binary buffers.

Timing and asynchronous operations

Events, timers, network requests are all asynchronous and separate from each other and exist both in Node and in the browser. You have to be able to understand how to work with callbacks or promises.

Accessibility

The interactions imposed by JavaScript can present accessibility barriers. A serious JavaScript developer is already familiar with WCAG 2.0 and knows how to work within its recommendations or when to push back on violating business requirements.

Security

You need to have at least a basic understanding of security violations, security controls, and privacy. You don't need to be a CISSP, but you need to be able to supply recommendations and avoid obvious failures. If you cannot get this right in the most basic sense you aren't a serious developer.

Data structures

You need to understand how to organize data in a way that allows the fastest possible execution without compromising maintenance. This is something that is learned through academic study and repeated experience writing applications.

Presentation and semantics

You really need to have a basic understanding how to properly organize the content your users will consume and how to present in a consumable way efficiently. This is something almost completely learned from experience only. You might think CSS and HTML are simple skills that can be picked up when needed, but you would be absolutely wrong.

Knowing when to avoid the bullshit

Many developers lack the years of experience to be confident in their performance.... so some of these developers will try to fake it. Don't be an imposter, because everybody will see straight through it. Hoping mountains of abstractions, tooling, frameworks, compilers, and other bullshit will save you just bogs down your application and screws over your teammates. If you aren't confident then be honest about that and seek mentorship or get involved with open source software outside of work.