    function baseMergeDeep(object, source, key, srcIndex, mergeFunc, customizer, stack) {
      var objValue = safeGet(object, key),
          srcValue = safeGet(source, key),
          stacked = stack.get(srcValue);

      if (stacked) {
        assignMergeValue(object, key, stacked);
        return;
      }
      var newValue = customizer
        ? customizer(objValue, srcValue, (key + ''), object, source, stack)
        : undefined;

      var isCommon = newValue === undefined;

      if (isCommon) {
        var isArr = isArray(srcValue),
            isBuff = !isArr && isBuffer(srcValue),
            isTyped = !isArr && !isBuff && isTypedArray(srcValue);

        newValue = srcValue;
        if (isArr || isBuff || isTyped) {
          if (isArray(objValue)) {
            newValue = objValue;
          }
          else if (isArrayLikeObject(objValue)) {
            newValue = copyArray(objValue);
          }
          else if (isBuff) {
            isCommon = false;
            newValue = cloneBuffer(srcValue, true);
          }
          else if (isTyped) {
            isCommon = false;
            newValue = cloneTypedArray(srcValue, true);
          }
          else {
            newValue = [];
          }
        }
        else if (isPlainObject(srcValue) || isArguments(srcValue)) {
          newValue = objValue;
          if (isArguments(objValue)) {
            newValue = toPlainObject(objValue);
          }
          else if (!isObject(objValue) || (srcIndex && isFunction(objValue))) {
            newValue = initCloneObject(srcValue);
          }
        }
        else {
          isCommon = false;
        }
      }
      if (isCommon) {
        // Recursively merge objects and arrays (susceptible to call stack limits).
        stack.set(srcValue, newValue);
        mergeFunc(newValue, srcValue, srcIndex, customizer, stack);
        stack['delete'](srcValue);
      }
      assignMergeValue(object, key, newValue);
    }