Most explanations of these concepts stop at the definition. Scope gets a rule about hoisting. Closures get a counter function that increments a number nobody would ever ship. The event loop gets a diagram. any versus unknown gets a one-line rule. Generics get a toy example with numbers and strings that never shows up in a real codebase.
That's enough to answer a question in an interview. It's not enough to actually recognize these patterns when they show up in your own code, which is the thing that matters once you're past the interview and actually shipping something.
This is the first in a short series working through concepts that come up constantly in interviews, explained the way I'd actually explain them to someone on my team, with real examples from production code, not just the textbook version.
var, let, and const
var, let, and const are the three ways to declare a variable in JavaScript. var is function-scoped and can be redeclared and reassigned freely. let is block-scoped and can be reassigned but not redeclared in the same scope. const is block-scoped and can't be reassigned after its initial value is set, though an object or array it points to can still be mutated internally.
