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Question 119

Which call returns true under the non-coercing rules of Number.isNaN?

  1. Number.isNaN("hello")
  2. Number.isNaN(undefined)
  3. Number.isNaN(NaN)Correct answer
  4. Number.isNaN("NaN")

Explanation

Number.isNaN returns true only when its argument is already the Number value NaN, so Number.isNaN(NaN) succeeds. It does not coerce the string hello or undefined before testing, unlike the coercing behavior associated with the global isNaN function.

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Question 119: Which call returns true under the non-coercing rules of… · JavaScript Fundamentals · Questena