Example2.js

// old interface

function Shipping() {
    this.request = function(zipStart, zipEnd, weight) {
        /**********/
        return '$49.75';
    }
}

// new interface

function AdvencedShipping() {
    this.login = function(credentials) {}
    this.setStart = function(start) {}
    this.setDestination = function(destination) {}
    this.calculate = function(weight) { return '$39.50'; }
}

function ShippingAdapter(credentials) {
    let shipping = new AdvencedShipping();

    shipping.login(credentials);

    return {
        request: function(zipStart, zipEnd, weight) {
            shipping.setStart(zipStart);
            shipping.setDestination(zipEnd);
            
            return shipping.calculate(weight);
        }
    }
}

let log = (function() {
   let log = "";
   
   return {
       add: function(msg) { log += msg + "\n";},
       show: function() { console.log(log); log = "";}
   }
})();

function run() {
    let shipping = new Shipping();
    let credentials = {token: "30a8-6ee1"};
    let adapter = new ShippingAdapter(credentials);

    let cost = shipping.request("78701", "10010", "2 lbs");
    log.add("Old cost: " + cost);
 
    // new shipping object with adapted interface
 
    cost = adapter.request("78701", "10010", "2 lbs");
 
    log.add("New cost: " + cost);
    log.show();
}

run();