merge.js

/**
 * Combine from left to right, 2 or more objects into a new single one.
 * Properties will be shallow copied. Those with the same name will be
 * overwriten by right most object.
 *
 * @tag Object
 * @signature ( ...source: Object[] ): Object
 *
 * @param   {Object[]}  source  Array of objects
 *
 * @return  {Object}
 *
 * @example
 * merge({a: "lorem"}, {b: "ipsum", c: 41}, {c: 42, b: undefined})
 * // => { a: "lorem", b: "ipsum", c: 42 }
 */
module.exports = (...sources) => {
  const result = {}

  for (let i = 0, length = sources.length; i < length; i++) {
    const sourceEntries = Object.entries(sources[i])

    for (
      let j = 0, sourceEntriesLength = sourceEntries.length;
      j < sourceEntriesLength;
      j++
    ) {
      const [key, value] = sourceEntries[j]

      if (value !== undefined) {
        result[key] = value
      }
    }
  }

  return result
}