lodash/internal/baseMap.js

define(['./baseEach', './getLength', './isLength'], function(baseEach, getLength, isLength) {

  /**
   * The base implementation of `_.map` without support for callback shorthands
   * and `this` binding.
   *
   * @private
   * @param {Array|Object|string} collection The collection to iterate over.
   * @param {Function} iteratee The function invoked per iteration.
   * @returns {Array} Returns the new mapped array.
   */
  function baseMap(collection, iteratee) {
    var index = -1,
        length = getLength(collection),
        result = isLength(length) ? Array(length) : [];

    baseEach(collection, function(value, key, collection) {
      result[++index] = iteratee(value, key, collection);
    });
    return result;
  }

  return baseMap;
});