code: function mergeArrays(source, target) {
    for (let i = 0; i < source.length; i++) {
      // If the item is not yet in the target array, add it
      if (target.indexOf(source[i]) === -1) {
        target.push(source[i])
      }
    }
  
    return target
  }
docs: Merge two arrays
  
  @private
  @param     {Array}    source     Source to merge
  @param     {Array}    target     Target to merge into
  @param     {Object}   opts       Options for the merge
  @return    {Array}