Angular has a powerful dependency injection system. Learn how to use it so that your code complies with the Dependency Inversion Principle.
Dependency Inversion in Angular
Using Generator Functions as Iterators
If you're getting a little more advanced in your JavaScript, you may have started using the [Symbol.iterator] to make your objects iterable. Using a generator function allows for much more idiomatic looking code and saves you from having to return an object that conforms to the iterable protocol.
Make large numbers human-readable
Reading a number like 1000000000000 on a line of code may be a breeze for your computer but is next to impossible for a human to do without getting a headache or nose bleed. What can we do to make large numbers more readable to the human eye?
Using Math on BigInt
BigInt is a relatively new addition to JavaScript and many aren't familiar with it. This was my case until recently. While working on the Closest Number puzzle on condingame.com, I found myself having to deal with numbers of sizes as big as 10^1000.
Accessing items in 2D Arrays
Accessing items in a 2D array can sometimes be a pain. I have created an Array2D class that extends Array and eases some of that pain.