Number.isFinite('') and Number.isNaN('') returns false, isFinite('') and isNaN('') returns true, the global versions of isFinite and isNaN first coerce their in

Number.isFinite('') and Number.isNaN('') returns false, isFinite('') and isNaN('') returns true, the global versions of isFinite and isNaN first coerce their input to number, no '+' necessary. Hence the heading "Confusing Special Case Behavior" in the mdn docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/isNaN#confusing_special-case_behavior https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...