Question 08 / 31

Which assignments affect parameters, locals, and globals?

Topic: Lexical scopeDifficulty: Intermediate

The parameter a and local b shadow globals, while c resolves to the outer binding.

Predict the output

After fn returns, determine which of the three global values changed.

var a = 12, b = 13, c = 14
function fn(a) {
  a = 0
  var b = 0
  c = 0
}
fn(a)
console.log(a)
console.log(b)
console.log(c)

Reveal the answer and explanation

12
13
0

The parameter a is a local binding initialized from the argument value 12. Assigning 0 to it does not modify global a.

The var declaration creates a local b, so b = 0 also leaves global b unchanged.

There is no local c. Name resolution reaches the global c binding, so c = 0 changes the value observed after the call.

The example passes a primitive number; no shared object mutation is involved.