Edit in JSFiddle

require.config({baseUrl: "http://ibm-js.github.io/libraries/master/"});
require(["liaison-build/layer"], function () {
    require(["liaison/ObservableArray"], function (ObservableArray) {
        var records = [],
            observableArray = new ObservableArray("a", "b", "c"),
            h = ObservableArray.observe(observableArray, function (changeRecords) {
                records.push.apply(records, changeRecords);
            });
        document.querySelector("input").addEventListener("click", function () {
            observableArray.set("length", 1); // Ends up removing the last two entries
            h.deliver();
            document.querySelector("pre").innerHTML = JSON.stringify(records, null, 4);
        });
    });
});