createOrderString.js

const basicSurround = curry((char, text) => `${char}${text}${char}`);

const snglQt = basicSurround(`'`);

const dblQt = basicSurround(`"`);

const OrderPrefixTmplt = jsonKey => `${dblQt(jsonKey)}->>`;

const OrderBaseTmplt = (field, dir) => `${field} ${dir}`;

const OrderTmplt = ( [field, dir, jsonKey] ) => isNil(jsonKey)
  ? OrderBaseTmplt(dblQt(field), dir)
  : `${OrderPrefixTmplt(jsonKey)}${OrderBaseTmplt(snglQt(field), dir)}`
;

// Returns 3 item array that can be applied to OrderTmplt
const makeOrderTmpltTuple = ( [fieldName, dir] ) => {
  // Because Array destructuring returns undefined for unreturnable
  // positions, placing the jsonKey assignment at the end ensures
  // that it either returns undefined or the actual name of the
  // desired json keyname in the last position of the array
  let [field, jsonKey] = reverse(
    split('.', fieldName)
  );

  return [
    field,
    dir,
    jsonKey,
  ];
};

const createOrderStr = compose(
  OrderTmplt,
  makeOrderTmpltTuple
);

const createOrder = compose(
  join(', '),
  map(createOrderStr),
  propOr([['createdAt', 'DESC']], 'order')
);

// -- process
const order = [
  ['data.date', 'DESC'],
  ['data.title', 'ASC'],
  ['updatedAt', 'DESC']
];

const data = {
  order
};

createOrder(data);