JSFiddle - React, Tailwind, and code Playground

JavaScript

var vm = {
    datum: ko.observable(),
    blocker: ko.computed({
        read: function() {
            throw new Error("Serialization of this model is prohibited.");
            this.valueHasMutated();
        },
        deferEvaluation: true,
        owner: this
    })
};

try {
  console.log("toJSON", ko.toJSON(vm)); // error, as expected
} catch (err) {
   console.log("toJSON failed, as expected");
}
 
console.log("toJS", ko.toJS(vm)); // serializes everything but the blocker.