Question

If we have an object r and want to know if it is a Range object, we can write ______________

(a) r typeof Range

(b) r is Range

(c) r equals Range

(d) r instanceof Range

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Answer 1

The correct answer is (d) r instanceof Range

Explanation: To know the range object r instanceof range is used. The r instanceof Range returns true if r inherits from Range.prototype. The instanceof operator does not actually check whether r was initialized by the Range constructor.