lodash-es/_shuffleSelf.js

import baseRandom from './_baseRandom.js';

/**
 * A specialized version of `_.shuffle` which mutates and sets the size of `array`.
 *
 * @private
 * @param {Array} array The array to shuffle.
 * @param {number} [size=array.length] The size of `array`.
 * @returns {Array} Returns `array`.
 */
function shuffleSelf(array, size) {
  var index = -1,
      length = array.length,
      lastIndex = length - 1;

  size = size === undefined ? length : size;
  while (++index < size) {
    var rand = baseRandom(index, lastIndex),
        value = array[rand];

    array[rand] = array[index];
    array[index] = value;
  }
  array.length = size;
  return array;
}

export default shuffleSelf;