Working with Lists and Collections

Seat Reservation example

by Diya_Khan

HTML

<h2>Your seat reservations (<span data-bind="text: seats().length"></span>)</h2>

<table>
    <thead><tr>
        <th>Passenger name</th><th>Meal</th><th>Surcharge</th><th></th>
    </tr></thead>
    <tbody data-bind="foreach: seats">
        <tr>
            <td><input data-bind="value: name" /></td>
            <td><select data-bind="options: $root.availableMeals, value: meal, optionsText: 'mealName'"></select></td>
            <td data-bind="text: formattedPrice"></td>
            <td><a href="#" data-bind="click: $root.removeSeat">Remove</a></td>
        </tr>    
    </tbody>
</table>
<h3 data-bind="visible: totalSurcharge() > 0">
    Total surcharge: $ <span data-bind="text: totalSurcharge().toFixed(2)"></span>
</h3>
<button data-bind="enable: seats().length < 5, click: addSeat">Reserve another seat</button>

JavaScript

// Class to represent a row in the seat reservations grid
function SeatReservation(name, initialMeal) {
    var self = this;
    self.name = name;
    self.meal = ko.observable(initialMeal);

    self.formattedPrice = ko.computed(function() {
        var price = self.meal().price;
        return price ? "$" + price.toFixed(2) : "None";        
    });    
}

// Overall viewmodel for this screen, along with initial state
function ReservationsViewModel() {
    var self = this;

    // Non-editable catalog data - would come from the server
    self.availableMeals = [
        { mealName: "Standard (sandwich)", price: 0 },
        { mealName: "Premium (lobster)", price: 34.95 },
        { mealName: "Ultimate (whole zebra)", price: 290 }
    ];    

    // Editable data
    self.seats = ko.observableArray([
        new SeatReservation("Steve", self.availableMeals[0]),
        new SeatReservation("Bert", self.availableMeals[0])
    ]);

    // Operations
    self.addSeat = function() {
        self.seats.push(new SeatReservation("", self.availableMeals[0]));
    }
    
    self.removeSeat = function(seat){
        self.seats.remove(seat)
    }
    
        self.totalSurcharge = ko.computed(function(){
            var total = 0;
            for(var i=0;i<self.seats().length;i++)
                total += self.seats()[i].meal().price;
            return total;
        });
}

ko.applyBindings(new ReservationsViewModel());