JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/SteveSanderson/knockout.mapping/master/build/output/knockout.mapping-latest.js"></script>

JavaScript

function viewmodel() {
    var self = this;

    this.ignore = ko.observable("ignore");
    this.copy = ko.observable("copy");

    this.toJS = function () {
        var mapping = {
            'ignore': ["ignore", "toJS"]
        }

        return ko.mapping.toJS(self, mapping);
    };
};

var vm = new viewmodel();
ko.applyBindings(vm);

console.log(vm.toJS());