joinSelect.js

const juxtMerge = (fnList) => compose(
    mergeAll,
    juxt(fnList)
);

// given an object, a foreignKey (name), and a lookup object
// containing data keyed to the foreignKey,
// return the data of the lookup, or a fallback value
const propOfPropOr = (fallback, foreignKey, lookup) => (item) => propOr(
    fallback,
    prop(foreignKey, item),
    lookup
);

// return either a select subset of keys from a lookup,
// or an empty object in case of failure
const safeSelectDetail = (selectKeys, foreignKey, lookup) => (item) => pick(
    selectKeys,
    propOfPropOr({}, foreignKey, lookup)(item)
);

// returns a new list enhanced by the selected keys of a lookup object
// (de-normalize a data set with its foreign key data)
const joinSelect = ({ selectKeys, foreignKey, lookup }) => map(
    juxtMerge([
        identity,
        safeSelectDetail(selectKeys, foreignKey, lookup)
    ])
); // ([1,2,3])


const orderData = [
  {id: '123', recipient: 'ryan', order: 'pizza'},
  {id: '124', recipient: 'alex', order: 'pizza'},
  {id: '125', recipient: 'alex', order: 'hotDog'},
  {id: '126', recipient: 'dave', order: 'hamburger'},
  {id: '127', recipient: 'anne', order: 'soup'},
];

const foodData = {
  pizza: { name: 'pizza', price: 15 },
  hotDog: { name: 'hotDog', price: 6 },
  hamburger: { name: 'hamburger', price: 9 },
};

const billingData = {
  ryan: { address: '123 Mockingbird Ln', cc: 9876 },
  alex: { address: '125 Mockingbird Ln', cc: 9876 },
  dave: { address: '127 Mockingbird Ln', cc: 9876 },
};

const multiJoinData = [
  {
    selectKeys: ['address'],
    foreignKey: 'recipient',
    lookup: billingData,
  },
  {
    selectKeys: ['price', 'ingredients'],
    foreignKey: 'order',
    lookup: foodData,
  }
];

// joinSelect(
//   multiJoinData[0]
// )(
  joinSelect(
    multiJoinData[1]
  )(orderData)
// );

// apply(
//   compose,
//   map(joinSelect, multiJoinData)
// )(orderData)