lodash/lodash.partition/index.js

/**
 * lodash 4.3.0 (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright jQuery Foundation and other contributors <https://jquery.org/>
 * Released under MIT license <https://lodash.com/license>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 */
var baseEach = require('lodash._baseeach'),
    baseIteratee = require('lodash._baseiteratee');

/**
 * A specialized version of `baseAggregator` for arrays.
 *
 * @private
 * @param {Array} array The array to iterate over.
 * @param {Function} setter The function to set `accumulator` values.
 * @param {Function} iteratee The iteratee to transform keys.
 * @param {Object} accumulator The initial aggregated object.
 * @returns {Function} Returns `accumulator`.
 */
function arrayAggregator(array, setter, iteratee, accumulator) {
  var index = -1,
      length = array.length;

  while (++index < length) {
    var value = array[index];
    setter(accumulator, value, iteratee(value), array);
  }
  return accumulator;
}

/**
 * Aggregates elements of `collection` on `accumulator` with keys transformed
 * by `iteratee` and values set by `setter`.
 *
 * @private
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} setter The function to set `accumulator` values.
 * @param {Function} iteratee The iteratee to transform keys.
 * @param {Object} accumulator The initial aggregated object.
 * @returns {Function} Returns `accumulator`.
 */
function baseAggregator(collection, setter, iteratee, accumulator) {
  baseEach(collection, function(value, key, collection) {
    setter(accumulator, value, iteratee(value), collection);
  });
  return accumulator;
}

/**
 * Creates a function like `_.groupBy`.
 *
 * @private
 * @param {Function} setter The function to set accumulator values.
 * @param {Function} [initializer] The accumulator object initializer.
 * @returns {Function} Returns the new aggregator function.
 */
function createAggregator(setter, initializer) {
  return function(collection, iteratee) {
    var func = isArray(collection) ? arrayAggregator : baseAggregator,
        accumulator = initializer ? initializer() : {};

    return func(collection, setter, baseIteratee(iteratee), accumulator);
  };
}

/**
 * Creates an array of elements split into two groups, the first of which
 * contains elements `predicate` returns truthy for, the second of which
 * contains elements `predicate` returns falsey for. The predicate is
 * invoked with one argument: (value).
 *
 * @static
 * @memberOf _
 * @since 3.0.0
 * @category Collection
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Array|Function|Object|string} [predicate=_.identity]
 *  The function invoked per iteration.
 * @returns {Array} Returns the array of grouped elements.
 * @example
 *
 * var users = [
 *   { 'user': 'barney',  'age': 36, 'active': false },
 *   { 'user': 'fred',    'age': 40, 'active': true },
 *   { 'user': 'pebbles', 'age': 1,  'active': false }
 * ];
 *
 * _.partition(users, function(o) { return o.active; });
 * // => objects for [['fred'], ['barney', 'pebbles']]
 *
 * // The `_.matches` iteratee shorthand.
 * _.partition(users, { 'age': 1, 'active': false });
 * // => objects for [['pebbles'], ['barney', 'fred']]
 *
 * // The `_.matchesProperty` iteratee shorthand.
 * _.partition(users, ['active', false]);
 * // => objects for [['barney', 'pebbles'], ['fred']]
 *
 * // The `_.property` iteratee shorthand.
 * _.partition(users, 'active');
 * // => objects for [['fred'], ['barney', 'pebbles']]
 */
var partition = createAggregator(function(result, value, key) {
  result[key ? 0 : 1].push(value);
}, function() { return [[], []]; });

/**
 * Checks if `value` is classified as an `Array` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @type {Function}
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is correctly classified,
 *  else `false`.
 * @example
 *
 * _.isArray([1, 2, 3]);
 * // => true
 *
 * _.isArray(document.body.children);
 * // => false
 *
 * _.isArray('abc');
 * // => false
 *
 * _.isArray(_.noop);
 * // => false
 */
var isArray = Array.isArray;

module.exports = partition;