5 ms·

NaN is incredibly useful, but I'm not so sure that 1/"a" = NaN is a great idea.

• grayrest 14y ago
  Strings that arent numeric are type coerced into NaN. Using unary plus to coerce to number: +"2" is the primitive number 2 while +"a" is NaN and per the floating point spec, any arithmetic operation on NaN results in NaN. The correct though unintuitive way to check for NaN is `(x === x) === false`. NaN is a number per the IEEE 754. The majority of Javascript WTFs are due to type coercion. Use triple equals and check your inputs to avoid.
  • some-1 14y ago
    No, the correct way is to use the global function isNaN(x);
    • grayrest 14y ago
      isNaN will return true for NaN and all values that coerce to it. The equals check will test ONLY for NaN itself: var x = "a"; isNaN(x); // true (x === x) === false // false x = NaN isNaN(x); // true (x === x) === false // true