Classes: It looks like there are a lot of ways to use classes and methods within those. Learning about the prototype chain and inheritance was interesting too.
Destructuring: Destructuring looks very useful too. Like mapping through an array or object and only using what you need.
Rest: Rest is how you can declare something and leave room for more variables to be added in as needed by user input.
Spread: Spread allows you to access the different elements in an array from within arguments.
Function Defaults: Default function parameters seem like a good idea in case the user doesn’t pass in all of the needed data, or to have just in case another computer doesn’t give everything that’s expected.