Variables

Question 1

What is var?

Answer 1

A statement that declares function-scoped or globally-scoped variables, optionally initializing each to a value.

Variables declared with var are hoisted (they are processed before any code execution).

Only the variable declaration is hoisted, not its initialization.

Question 2

What is let?

Answer 2

A statement that declares re-assignable, block-scoped local variables, optionally initializing each to a value.

Question 3

What is const?

Answer 3

A statement that declares block-scoped local variables. The value of a constant can’t be changed through reassignment using the assignment operator, but if a constant is an object, its properties can be added, updated or removed.

Question 4

What is the TDZ?

Answer 4

Temporal Dead Zone. A variable is said to be in the TDZ from the start of the block until code execution reaches the place where the variable is declared and initialized.

Question 5

What is hoisting?

Answer 5

Process in which the parser/interpreter appears to move the declaration of functions, variables, classes or imports to the top of their scope, prior to the execution of the code.

Question 6

What is nullish coalescing?

Answer 6

A logical operator (??) that returns its right-hand side operand when its left-hand side operand is null or undefined. Otherwise, it returns its left-hand side operand.