JAVASCRIPT

isNaN

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

isNan

const fail = 10 / "zero"; 
console.log(fail); //   NaN (Not a Number)
console.log(isNaN(fail)); // true
console.log(isNaN(10)); // false
console.log(isNaN('10')); // false
console.log(isNaN('blabla')); // true
console.log(isNaN(true)); // false
console.log(1.7976931348623157e+308 * 1000); //  Infinity
console.log(1.7976931348623157e+308 * -1000); // - Infinity
console.log(10 / 0); // Infinity
console.log(isFinite(123)); // true

isNaN

isNaN("Hello")  // Returns true
isNaN(345)   // Returns false
isNaN('1')  // Returns false, since '1' is converted to Number type which results in 0 ( a number) 
isNaN(true) // Returns false, since true converted to Number type results in 1 ( a number)
isNaN(false) // Returns false
isNaN(undefined) // Returns true