Tutorial.Value

function run_value(root) {
    value = new TK.Value({
        size: 10,
        value: 123.97,
        format: TK.FORMAT("%.3f Hz"),
        set: function (val) { val = parseFloat(val); console.log("the value was set to " + val); return val; }
    });
    root.append_child(value);
}