JavaScript Closures and Scope 2

Question 1

What is the scope of a variable declared with `var` inside a function?

Accepted Answer

Function scope

Answer

Variables declared with `var` are function-scoped, meaning they are accessible anywhere within the function they are declared in, regardless of the block (if/else, loops) they appear in.

Question 2

In JavaScript, what is a closure?

Accepted Answer

A function that has access to variables from its outer (enclosing) scope even after that scope has returned

Answer

A closure is created when a function 'closes over' variables from its lexical environment. Even after the outer function returns, the inner function retains access to the outer function's variables.

Question 3

What will `console.log(x)` output if `x` is declared with `var` after the log statement?

Accepted Answer

undefined

Answer

`var` declarations are hoisted to the top of their scope, but only the declaration — not the initialization. So accessing a `var` before its assignment returns `undefined`, not a ReferenceError.

Question 4

What is the Temporal Dead Zone (TDZ)?

Accepted Answer

The time between entering a block scope and a `let`/`const` declaration being initialized

Answer

The Temporal Dead Zone is the region in a block scope where `let` or `const` variables are hoisted but not yet initialized. Accessing them in this zone throws a `ReferenceError`.

Question 5

What is a common use of closures — creating private variables?

Accepted Answer

Wrapping state in an outer function scope that inner functions close over

Answer

Closures allow you to create private state by defining variables in an outer function. Inner functions close over those variables and are returned as the public API — outside code can't directly access the closed-over variables.

JavaScript Practice Test

JavaScript Practice Test

JavaScript Closures and Scope 2