Knockout doesn't update when the array changes?

Question

I have a Knockout UI where I am putting objects into observables. Once you click an add to cart button that updates the object, the ui doesn't update. Once you refresh the page it will update.

I have heard to a lot of people having this TYPE of issue, but I haven't seen anything pertaining to this case.

Global Vars:

var koCart, koQuantity, koTotal;

Function:

function updateCart() {
   **parse data ** 
    //assign data to observables
    koCart = ko.observableArray(domecart)
    koQuantity = ko.observable(quantity)
    koTotal = ko.observable(total)
}

View Model:

function viewModel() {
        self = this;
        this.newcart = koCart();
        this.total = koTotal();
        this.quantity = koQuantity();
}
var element = document.getElementById('cart'); 
var element2 = $('.floatingTab')[0];
var app = new viewModel();
ko.applyBindings(app, element);
ko.applyBindings(app, element2);

Cart with KO Bindings

<nav class="cbp-spmenu cbp-spmenu-vertical cbp-spmenu-right shopify-buy__cart" id="cbp-spmenu-s2">
        <div class="shopify-buy__cart__header">
            <h2 class="shopify-buy__cart__title">Cart</h2>
            <button class="shopify-buy__btn--close">
                <span aria-role="hidden" id="x-menu">×</span>
            </button>
        </div>
        <div id="cart" class="shopify-buy__cart-scroll">
            <div class="shopify-buy__cart-items" data-bind="foreach: newcart">
                <div class="shopify-buy__cart-item">
                    <div data-bind="style: { 'background-image': 'url(' + images + ')'}" class="shopify-buy__cart-item__image" alt="Product" style="background-repeat:no-repeat;background-size: contain;"></div>
                    <span class="shopify-buy__cart-item__title" data-bind="text: name"></span>
                    <span class="shopify-buy__cart-item__price" data-bind="text: price "></span>
                    <div class="shopify-buy__quantity-container">
                        <button class="shopify-buy__btn--seamless shopify-buy__quantity-decrement" type="button">
                            <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path d="M4 7h8v2H4z"></path></svg>
                        </button>
                        <input class="shopify-buy__quantity shopify-buy__cart-item__quantity-input" type="number" min="0" aria-label="Quantity" data-bind="attr: {value: quantity}" style="height: 30px; border:solid 1px #d3dbe2 !important;padding-left:13px;" />
                        <button class="shopify-buy__btn--seamless shopify-buy__quantity-increment" type="button" databind="click: addToCard(id)" >
                            <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path d="M12 7H9V4H7v3H4v2h3v3h2V9h3z"></path></svg>
                        </button>

                    </div>
                </div>
            </div> 
            <div class="shopify-buy__cart-bottom">
                <p class="shopify-buy__cart__subtotal__text" >SUBTOTAL</p>
                <p class="shopify-buy__cart__subtotal__price"data-bind="text: total"></p>
                <p class="shopify-buy__cart__notice">Shipping and discount codes are added at checkout.</p>
                <button class="shopify-buy__btn shopify-buy__btn--cart-checkout" type="button">CHECKOUT</button>
            </div>
        </div>
    </nav>

Also, the error being thrown is, koCart is not a function.

Answer 1

I would avoid using the global variables like that and include everything in a properly constructed viewmodel. You might do something like this where you first define your observables and then populate them from within your viewmodel:

function viewModel() {
    var self = this;
    self.newcart = ko.observableArray();
    self.total = ko.observable();
    self.quantity = ko.observable();

    self.updateCart = function() {
        **parse data ** 
        //assign data to observables
        self.newcart(domecart)
        self.quantity(quantity)
        self.total(total)
    }
}

var element = document.getElementById('cart'); 
var element2 = $('.floatingTab')[0];
var app = new viewModel();
ko.applyBindings(app, element);
ko.applyBindings(app, element2);

This does depend on how you get your data and when you need to call the updateCart function. Doing this could prove benefical as the update function could be in a computed that will automatically update through the user interaction in the UI.