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  1. JavaScript Objects & Arrays
  2. Introducing JavaScript objects
  3. Build-in objects

isNaN()

PreviousBuild-in objectsNextRegExp

Last updated 4 years ago

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The isNaN() function determines whether a value is or not. Because coercion inside the isNaN function can be , you may alternatively want to use .

function milliseconds(x) {
  if (isNaN(x)) {
    return 'Not a Number!';
  }
  return x * 1000;
}

console.log(milliseconds('100F'));
// expected output: "Not a Number!"

console.log(milliseconds('0.0314E+2'));
// expected output: 3140
NaN
surprising
Number.isNaN()