text: /*
   * Licensed to Elasticsearch B.V. under one or more contributor
   * license agreements. See the NOTICE file distributed with
   * this work for additional information regarding copyright
   * ownership. Elasticsearch B.V. licenses this file to you under
   * the Apache License, Version 2.0 (the "License"); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  const uniqueConcat = (arrayA, arrayB) => arrayB.reduce((acc, key) => (
    acc.includes(key)
      ? acc
      : acc.concat(key)
  ), arrayA);
  
  /**
   * Assign the keys from both objA and objB to target after passing the
   * current and new value through merge as `(target[key], source[key])`
   * @param  {Object} objA
   * @param  {Object} objB
   * @param  {Function} merge
   * @return {Object} target
   */
  export function mergeWith(objA, objB, merge) {
    const target = {};
    const keys = uniqueConcat(Object.keys(objA), Object.keys(objB));
    for (const key of keys) {
      target[key] = merge(objA[key], objB[key]);
    }
    return target;
  }
  