JavaScript · Senior · Question 48 of 75

What is the Temporal Dead Zone for default parameters?

function f(a = b, b = 1) { return a; }
f();

✓Correct answer: ReferenceError: parameter b isn't initialized yet when a is evaluated
2Returns 1: default parameters are evaluated in any order
3Returns undefined: b is hoisted with the value undefined

Explanation

Parameters are initialized left to right and behave like let: accessing a not-yet-initialized parameter is a TDZ error. In the reverse order (a = 1, b = a) it works. Default values are evaluated on every call, not once.

What is the Temporal Dead Zone for default parameters?

Explanation

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