How to get to the DOM element from a knockout binding?

Question

I have bound a DOM element to a viewModel using knockout. When I change a property on the underlying model it changes the DOM - all ok.

However, is there a way to get to the bound DOM element so I can add a class to it when the underlying model gets updated externally?

I have used custom binding which gives me access to the DOM element but I was wondering if there is a simpler way directly from the viewModel's bound property?

Thanks

sample code (TypeScript)

SetMyCell(row: number, newValue: any) {

    var ditem = this._DataItems[row];

    // update the actual value    
    ditem.Producer(newValue);

    // Now I wish to decorate the DOM item this Producer property is 
    // bound to with a class. How to go about that?

}

Answer 1

You can abuse the visible binding for example to execute a function passing the $element and $data.

<span data-bind="visible: func1($element, $data)">Test span</span>

look at this fiddle

I know you mention above that you don't want to use a custom binding but i still want to point out this option. although i am using a custom binding the logic for modifying the element will still happen in the viewmodel when the external changes happen.

ko.bindingHandlers.widget = {
    init: function (element, valueAccessor, allBindings, viewModel, bindingContext) {
        var elemObservable = valueAccessor();
        if (ko.isObservable(elemObservable)) {
            elemObservable(element);
        }
    }
};

var vm = function () {
    var self = this;
    .....
    self.spanElement = ko.observable();
    self.btnClick = function (){
        var elem = self.spanElement();
        $(elem).html("This is the span element");
    };
    ......
};

and the html would be

<button data-bind="click: btnClick">change element text or something else</button>
<span data-bind="widget: spanElement"></span>

I have updated the fiddle so you can see it in action