This method is like `_.uniq` except that it accepts `iteratee` which is
invoked for each element in `array` to generate the criterion by which
uniqueness is computed. The order of result values is determined by the
order they occur in the array. The iteratee is invoked with one argument:
(value).

@static
@memberOf _
@since 4.0.0
@category Array
@param {Array} array The array to inspect.
@param {Function} [iteratee=_.identity]
The iteratee invoked per element.
@returns {Array} Returns the new duplicate free array.
@example

_.uniqBy([2.1, 1.2, 2.3], Math.floor);
// => [2.1, 1.2]

// The `_.property` iteratee shorthand.
_.uniqBy([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }, { 'x': 2 }]
function uniqBy(array, iteratee) {
  return (array && array.length)
    ? baseUniq(array, baseIteratee(iteratee, 2))
    : [];
}