objectify.js

/**
 * Convert cols and rows into an array of objects.
 * Will return array of objects mapping cols to row values.
 *
 * Repeated cols are mapped to array values.
 * 
 * @param {Array} cols The keys
 * @param {Array} rows the array of arrays of values
 * @return {Array} The rows as objects
 * @example
 *   objectify(
 *     ['name', 'email', 'email'],
 *     [
 *       ['Derp', '[email protected]', '[email protected]']
 *     ]
 *   )
 *   // => [{ name: 'Derp', email: ['[email protected]', '[email protected]'] }]
 */
function objectify (cols, rows) {
  // Create a map of key to fn(memo, key, val)
  const colMap = cols.reduce((colMap, key) => {
    if (colMap[key]) {
      colMap[key] = keyToArray
    } else {
      colMap[key] = keyToVal
    }
    return colMap
  }, {})

  return rows.map((row) => {
    // colMap[key] is a fn(memo, key, val)
    return cols.reduce((memo, key, i) => colMap[key](memo, key, row[i]), {})
  })
}