extend.js

'use strict';

/**
 * Merges to objects together, favoring the second object's properties.
 *
 * Details:
 * Overwrites `first` properties with `second` properties and adds `second`
 * properties if missing in `first`
 *
 * @param  {Object}  first
 * @param  {Object}  second
 * @param  {Boolean} deep   Deep-extend the objects
 * @return {Object}  The    merged objects
 */
function extend(first, second, deep) {
  var prop, value,
    result = {};

  // mirror the first object
  for (prop in first) {
    if (first.hasOwnProperty(prop)) {
      result[prop] = first[prop];
    }
  }

  for (prop in second) {
    if (second.hasOwnProperty(prop)) {
      value = second[prop];
      // deep extend an object's objects, but not arrays (when deep is truthy)
      if (typeof value === 'object' && deep && !Array.isArray(value)) {
        result[prop] = extend(result[prop], second[prop]);
      } else {
        result[prop] = second[prop];
      }
    }
  }

  return result;
}

module.exports = extend;