I’m building some dynamic table sorting. Looks like NaN values are messing with the sorting. For the sake of the example, let’s use an array of number-like strings. Try pasting this in your console.

(function() {
  var numbers = '19 26 63 twelve 83 106 hundred zero 12'.split(' ');
  return numbers.sort();
})();
// ["106", "12", "19", "26", "63", "83", "hundred", "twelve", "zero"]

The resulting array is as expected, since the values are still strings.

Let’s parse those values as integers, using a compare function in sort.

(function() {
  var numbers = '19 26 63 twelve 83 106 hundred zero 12'.split(' ');
  function parse( value ) {
    return parseInt( value );
  }
  return numbers.sort( function( a, b ) {
    return parse( a ) < parse( b );
  });
})();
// ["63", "26", "19", "twelve", "106", "83", "hundred", "zero", "12"]

This looks just random. I believe what’s happening is how a NaN value from parseInt('foo') messes with the comparison. Comparing any number with NaN will return false.

14 > NaN
// false
NaN > 14
// false

Oh JavaScript, you so cray.

My solution is to account for NaN in the parser.

(function() {
  var numbers = '19 26 63 twelve 83 106 hundred zero 12'.split(' ');
  function parse( value ) {
    value = parseInt( value );
    value = isNaN( value ) ? Infinity : value;
    return value;
  }
  return numbers.sort( function( a, b ) {
    return parse( a ) > parse( b );
  });
})();
// ["12", "19", "26", "63", "83", "106", "twelve", "hundred", "zero"]

You don’t have to munge NaN as Infinity, but this at least treats the value as a number that can be properly compared.