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 * Add a new item to an object
 * (c) 2018 Chris Ferdinandi, MIT License,
 * @param  {Object} obj   The original object
 * @param  {String} key   The key for the item to add
 * @param  {Any}    value The value for the new key to add
 * @param  {Number} index The position in the object to add the new key/value pair [optional]
 * @return {Object}       An immutable clone of the original object, with the new key/value pair added
var addToObject = function (obj, key, value, index) {

	// Create a temp object and index variable
	var temp = {};
	var i = 0;

	// Loop through the original object
	for (var prop in obj) {
		if (obj.hasOwnProperty(prop)) {

			// If the indexes match, add the new item
			if (i === index && key && value) {
				temp[key] = value;

			// Add the current item in the loop to the temp obj
			temp[prop] = obj[prop];

			// Increase the count


	// If no index, add to the end
	if (!index && key && value) {
		temp[key] = value;

	return temp;


// Original object
var lunch = {
  sandwich: 'turkey',
  drink: 'soda',
  chips: true

// Add to the end of the object
var lunchWithDessert = addToObject(lunch, 'dessert', 'cookie');

// Add between sandwich and drink
var lunchWithTopping = addToObject(lunch, 'topping', 'tomato', 1);

// Immutable copy of lunch
var lunchClone = addToObject(lunch);