internal/baseAt.js

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

  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
  var undefined;

  /**
   * The base implementation of `_.at` without support for strings and individual
   * key arguments.
   *
   * @private
   * @param {Array|Object} collection The collection to iterate over.
   * @param {number[]|string[]} [props] The property names or indexes of elements to pick.
   * @returns {Array} Returns the new array of picked elements.
   */
  function baseAt(collection, props) {
    var index = -1,
        length = collection.length,
        isArr = isLength(length),
        propsLength = props.length,
        result = Array(propsLength);

    while(++index < propsLength) {
      var key = props[index];
      if (isArr) {
        key = parseFloat(key);
        result[index] = isIndex(key, length) ? collection[key] : undefined;
      } else {
        result[index] = collection[key];
      }
    }
    return result;
  }

  return baseAt;
});