JavaScript Core

Understand closures with a counter factory

Understand how "this" works in different contexts

Understand prototypal inheritance

Understand variable and function hoisting

Understand lexical scope

Implement Function.prototype.call

Implement Function.prototype.apply

Implement Function.prototype.bind

Implement your own new operator

Implement Object.create

Implement the instanceof operator

Understand the difference between typeof and instanceof

Understand JavaScript execution context