JSFiddle - React, Tailwind, and code Playground

HTML

<div data-bind="test: name"></div>

JavaScript

model =
    {
        name: ko.observable("John"),
        xxx: ko.observable("x")
    };



ko.bindingHandlers.test =
{
    update: function  (element, valueAccessor, allBindingsAccessor, viewModel, bindingContext)
    {
        var b = document.getElementsByTagName("body")[0];
        var t = document.createElement("div");
        
        viewModel.xxx();
        
        t.innerHTML = valueAccessor()();
        b.appendChild(t);       
    }
};


ko.applyBindings(model);

model.name("Jim");
model.xxx(123123123);
model.name("Jane");