var baseExtremum = require('./internal/baseExtremum'),
    baseIteratee = require('./internal/baseIteratee'),
    gt = require('./gt');

/**
 * This method is like `_.max` except that it accepts `iteratee` which is
 * invoked for each element in `array` to generate the criterion by which
 * the value is ranked. The iteratee is invoked with one argument: (value).
 *
 * @static
 * @memberOf _
 * @category Math
 * @param {Array} array The array to iterate over.
 * @param {Function|Object|string} [iteratee=_.identity] The iteratee invoked per element.
 * @returns {*} Returns the maximum value.
 * @example
 *
 * var objects = [{ 'n': 1 }, { 'n': 2 }];
 *
 * _.maxBy(objects, function(o) { return o.a; });
 * // => { 'n': 2 }
 *
 * // using the `_.property` iteratee shorthand
 * _.maxBy(objects, 'n');
 * // => { 'n': 2 }
 */
function maxBy(array, iteratee) {
  return (array && array.length)
    ? baseExtremum(array, baseIteratee(iteratee), gt)
    : undefined;
}

module.exports = maxBy;
