ternary-operator.js

getMaxDateImpl =
  // Returns the maximum valid month day, given a year and a month.
  function (year, month) {
    return (
      indexOf([ 0, 2, 4, 6, 7, 9, 11 ], month) !== - 1 ?
        // January, March, May, July, August, October, or December.
        31 :
        indexOf([ 3, 5, 8, 10 ], month) !== - 1 ?
          // April, June, September, or November.
          30 :
          year % 400 === 0 || year % 100 !== 0 && year % 4 === 0 ?
            // February, leap year.
            29 :
            // February, common year.
            28
    );
  };