lodash/array/chunk.js

define(['../internal/baseSlice', '../internal/isIterateeCall'], function(baseSlice, isIterateeCall) {

  /** Native method references. */
  var ceil = Math.ceil;

  /* Native method references for those with the same name as other `lodash` methods. */
  var nativeMax = Math.max;

  /**
   * Creates an array of elements split into groups the length of `size`.
   * If `collection` can't be split evenly, the final chunk will be the remaining
   * elements.
   *
   * @static
   * @memberOf _
   * @category Array
   * @param {Array} array The array to process.
   * @param {number} [size=1] The length of each chunk.
   * @param- {Object} [guard] Enables use as a callback for functions like `_.map`.
   * @returns {Array} Returns the new array containing chunks.
   * @example
   *
   * _.chunk(['a', 'b', 'c', 'd'], 2);
   * // => [['a', 'b'], ['c', 'd']]
   *
   * _.chunk(['a', 'b', 'c', 'd'], 3);
   * // => [['a', 'b', 'c'], ['d']]
   */
  function chunk(array, size, guard) {
    if (guard ? isIterateeCall(array, size, guard) : size == null) {
      size = 1;
    } else {
      size = nativeMax(+size || 1, 1);
    }
    var index = 0,
        length = array ? array.length : 0,
        resIndex = -1,
        result = Array(ceil(length / size));

    while (index < length) {
      result[++resIndex] = baseSlice(array, index, (index += size));
    }
    return result;
  }

  return chunk;
});