JavaScript Adapter Design Pattern

The Adapter design pattern converts a class interface into another one the client expects. This pattern lets classes work together otherwise they couldn't because their interfaces are incompatible. The essence of the pattern is transferring an interface (object's properties and methods) to another. A common scenario of the pattern use is when new components and modules need to be integrated to work with existing ones in an application or when part of code is refactored with improved interface but still needs to work with old parts.

The example code presents an online flight ticket pricing calculation system. The old version used to make computations one way, now the improved one uses user identification and modernized pricing calculation. We introduce an adapter allowing the client program to continue working without any API changes by matching the old interface with the new one.

	// old interface
	function TicketPrice() {
		this.request = function(start, end, overweightLuggage) {
			// price calculation ...
			return "$150.34";

	// new interface
	function NewTicketPrice() {
		this.login = function(credentials) { /* process credentials */ };
		this.setStart = function(start) { /* set start point */ };
		this.setDestination = function(destination) { /* set destination */ };
		this.calculate = function(overweightLuggage) { 
			//price calculation ...
			return "$120.20"; 

	// adapter interface
	function TicketAdapter(credentials) {
		var pricing = new NewTicketPrice();
		return {
			request: function(start, end, overweightLuggage) {
				return pricing.calculate(overweightLuggage);

    var pricing = new TicketPrice();
    var credentials = { token: "30a8-6ee1" };
    var adapter = new TicketAdapter(credentials);
    // original ticket pricing and interface
    var price = pricing.request("Bern", "London", 20);
    console.log("Old price: " + price);
    // new ticket pricing with adapted interface
    price = adapter.request("Bern", "London", 20);
    console.log("New price: " + price);