function abs (mixed_number) {
  // http://kevin.vanzonneveld.net
  // +   original by: Waldo Malqui Silva
  // +   improved by: Karol Kowalski
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +   improved by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
  // *     example 1: abs(4.2);
  // *     returns 1: 4.2
  // *     example 2: abs(-4.2);
  // *     returns 2: 4.2
  // *     example 3: abs(-5);
  // *     returns 3: 5
  // *     example 4: abs('_argos');
  // *     returns 4: 0
  return Math.abs(mixed_number) || 0;
}

abs(4.2);

4.2

abs(-4.2);

4.2

abs(-5);

5