diffReturn.js

const apiResponse = [
  {first: 'Bob', favorite: 'The Clash'}, 
  {first: 'Linda', favorite: 'Ramones'}, 
  {first: 'Amy', favorite: 'The Clash'},
];
const friendConstants = ['Bob', 'Amy', 'James', 'Tiffany', 'Linda'];

friendConstants.reduce((acc, friend, idx, orgArray) => ({
  // Check for friend in apiResponse
  // if there pull them out otherwise we create a default objecct
  acc = {
    ...acc,
    [friend]: apiResponse.find({ first: friend }) || { first: friend, favorite: 'Unknown' },
  };
                                           
  // if we're on the last item in the array
  // return only the values of the acc
  // otherwise return acc and go to next iteration
  return idx === (orgArray.length - 1) ?
    Object.values(acc) :
    acc;
}), {});
// initalValue is an Object. But we'll get back an array
/*
=> [
  {first: 'Bob', favorite: 'The Clash'}, 
  {first: 'Amy', favorite: 'The Clash'},
  {first: 'James', favorite: 'Unknown'},
  {first: 'Tiffany, favorite: 'Unknown'},
  {first: 'Linda', favorite: 'Ramones'}, 
];  
*/