- Level 00: var, let, const
- Level 01: Classes, prototypical inheritance
- Level 02: Destructuring
- Level 03: Promise, async/await
- Level 04: null, undefined, empty
- Level 05: Closure vs Class
- Level 06: Currying
- Level 07: Microtasks, Macrotasks
- Level 08: Set, Map, Object
- Level 09: Reduce