gistfile1.js

    /**
     * The base implementation of `_.flatten` with added support for restricting
     * flattening and specifying the start index.
     *
     * @private
     * @param {Array} array The array to flatten.
     * @param {boolean} [isDeep] Specify a deep flatten.
     * @param {boolean} [isStrict] Restrict flattening to arrays-like objects.
     * @returns {Array} Returns the new flattened array.
     */
    function baseFlatten(array, isDeep, isStrict) {
      var index = -1,
          length = array.length,
          resIndex = -1,
          result = [];

      while (++index < length) {
        var value = array[index];
        if (isObjectLike(value) && isArrayLike(value) &&
            (isStrict || isArray(value) || isArguments(value))) {
          if (isDeep) {
            // Recursively flatten arrays (susceptible to call stack limits).
            value = baseFlatten(value, isDeep, isStrict);
          }
          var valIndex = -1,
              valLength = value.length;

          while (++valIndex < valLength) {
            result[++resIndex] = value[valIndex];
          }
        } else if (!isStrict) {
          result[++resIndex] = value;
        }
      }
      return result;
    }


/**
     * Creates an array of unique values, in order, from all of the provided arrays
     * using [`SameValueZero`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-samevaluezero)
     * for equality comparisons.
     *
     * @static
     * @memberOf _
     * @category Array
     * @param {...Array} [arrays] The arrays to inspect.
     * @returns {Array} Returns the new array of combined values.
     * @example
     *
     * _.union([1, 2], [4, 2], [2, 1]);
     * // => [1, 2, 4]
     */
    var union = restParam(function(arrays) {
      return baseUniq(baseFlatten(arrays, false, true));
    });



/**
     * The base implementation of `_.uniq` without support for callback shorthands
     * and `this` binding.
     *
     * @private
     * @param {Array} array The array to inspect.
     * @param {Function} [iteratee] The function invoked per iteration.
     * @returns {Array} Returns the new duplicate-value-free array.
     */
    function baseUniq(array, iteratee) {
      var index = -1,
          indexOf = getIndexOf(),
          length = array.length,
          isCommon = indexOf == baseIndexOf,
          isLarge = isCommon && length >= 200,
          seen = isLarge ? createCache() : null,
          result = [];

      if (seen) {
        indexOf = cacheIndexOf;
        isCommon = false;
      } else {
        isLarge = false;
        seen = iteratee ? [] : result;
      }
      outer:
      while (++index < length) {
        var value = array[index],
            computed = iteratee ? iteratee(value, index, array) : value;

        if (isCommon && value === value) {
          var seenIndex = seen.length;
          while (seenIndex--) {
            if (seen[seenIndex] === computed) {
              continue outer;
            }
          }
          if (iteratee) {
            seen.push(computed);
          }
          result.push(value);
        }
        else if (indexOf(seen, computed, 0) < 0) {
          if (iteratee || isLarge) {
            seen.push(computed);
          }
          result.push(value);
        }
      }
      return result;
    }