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Question 67

parent.active is true, and child was created with parent as its prototype. What does "active" in child evaluate to?

  1. undefined, because inherited properties have no boolean result
  2. false, because only child's own properties are searched
  3. true, because the inherited property is foundCorrect answer
  4. A TypeError, because in cannot inspect prototypes

Explanation

The in operator searches both the object and its prototype chain, so the inherited active property makes the test true. Saying false because child lacks an own property mistakes this operator for an ownership-only check.

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Question 67: parent.active is true, and child was created with parent as… · JavaScript Fundamentals · Questena