JavaScript Fundamentals

Which keyword declares a variable whose binding cannot be reassigned?

• Aconst — it creates a binding that cannot be reassigned after initialization
• Blet — it creates a binding that can be freely reassigned at any time
• Cvar — it declares a function-scoped binding that can be reassigned
• Dstatic — it declares a fixed binding shared across every program scope

Which of the following is a primitive data type in JavaScript?

• ABoolean — an immutable primitive value holding true or false
• BArray — an ordered, indexed collection of stored values
• CObject — a keyed collection of properties and their values
• DFunction — a callable, reusable block of program code

What is the difference between == and ===?

• A=== compares value and type with no coercion; == coerces types first
• B== compares value and type strictly; === also compares the memory address
• C=== works only on numbers, while == works on all other data types
• D== and === are identical; the extra sign is only a style preference

What is the main syntactic feature of an arrow function?

• AIt uses the => syntax and omits the function keyword for a shorter form
• BIt uses the -> syntax and omits the function keyword for a shorter form
• CIt requires the function keyword followed by a => before the body
• DIt must be declared with the arrow keyword before the parameter list

What does a closure keep access to after its outer function has returned?

• AThe variables of the scope it was created in, even after that scope exits
• BA snapshot copy of those variables, frozen at the moment of return
• CNothing, the variables are freed as soon as the outer function returns
• DOnly variables the inner function explicitly redeclares with let

Which runs first: Promise.resolve().then(f) or setTimeout(f, 0)?

• AThe .then callback — microtasks run before the next macrotask starts
• BsetTimeout — timers fire before any pending microtask can be processed
• CNeither is guaranteed — the engine may run either one first at random
• DBoth run in the same microtask, in the order they were scheduled