_equalArrays.js

define(['./_SetCache', './_arraySome', './_cacheHas'], function(SetCache, arraySome, cacheHas) {

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

  /** Used to compose bitmasks for value comparisons. */
  var COMPARE_PARTIAL_FLAG = 1,
      COMPARE_UNORDERED_FLAG = 2;

  /**
   * A specialized version of `baseIsEqualDeep` for arrays with support for
   * partial deep comparisons.
   *
   * @private
   * @param {Array} array The array to compare.
   * @param {Array} other The other array to compare.
   * @param {number} bitmask The bitmask flags. See `baseIsEqual` for more details.
   * @param {Function} customizer The function to customize comparisons.
   * @param {Function} equalFunc The function to determine equivalents of values.
   * @param {Object} stack Tracks traversed `array` and `other` objects.
   * @returns {boolean} Returns `true` if the arrays are equivalent, else `false`.
   */
  function equalArrays(array, other, bitmask, customizer, equalFunc, stack) {
    var isPartial = bitmask & COMPARE_PARTIAL_FLAG,
        arrLength = array.length,
        othLength = other.length;

    if (arrLength != othLength && !(isPartial && othLength > arrLength)) {
      return false;
    }
    // Assume cyclic values are equal.
    var stacked = stack.get(array);
    if (stacked && stack.get(other)) {
      return stacked == other;
    }
    var index = -1,
        result = true,
        seen = (bitmask & COMPARE_UNORDERED_FLAG) ? new SetCache : undefined;

    stack.set(array, other);
    stack.set(other, array);

    // Ignore non-index properties.
    while (++index < arrLength) {
      var arrValue = array[index],
          othValue = other[index];

      if (customizer) {
        var compared = isPartial
          ? customizer(othValue, arrValue, index, other, array, stack)
          : customizer(arrValue, othValue, index, array, other, stack);
      }
      if (compared !== undefined) {
        if (compared) {
          continue;
        }
        result = false;
        break;
      }
      // Recursively compare arrays (susceptible to call stack limits).
      if (seen) {
        if (!arraySome(other, function(othValue, othIndex) {
              if (!cacheHas(seen, othIndex) &&
                  (arrValue === othValue || equalFunc(arrValue, othValue, bitmask, customizer, stack))) {
                return seen.push(othIndex);
              }
            })) {
          result = false;
          break;
        }
      } else if (!(
            arrValue === othValue ||
              equalFunc(arrValue, othValue, bitmask, customizer, stack)
          )) {
        result = false;
        break;
      }
    }
    stack['delete'](array);
    stack['delete'](other);
    return result;
  }

  return equalArrays;
});