Number to ordinal suffix

OSCC · JavaScript, Math · Nov 13, 2020

Takes a number and returns it as a string with the correct ordinal indicator suffix.

  • Use the modulo operator (%) to find values of single and tens digits.
  • Find which ordinal pattern digits match.
  • If digit is found in teens pattern, use teens ordinal.
const toOrdinalSuffix = num => {
  const int = parseInt(num),
    digits = [int % 10, int % 100],
    ordinals = ['st', 'nd', 'rd', 'th'],
    oPattern = [1, 2, 3, 4],
    tPattern = [11, 12, 13, 14, 15, 16, 17, 18, 19];
  return oPattern.includes(digits[0]) && !tPattern.includes(digits[1])
    ? int + ordinals[digits[0] - 1]
    : int + ordinals[3];
};
toOrdinalSuffix('123'); // '123rd'

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