test.js

var _updating;
var _connection;

// connect to signalr hub
_connection = new signalR.HubConnectionBuilder().withUrl("/collabHub").build();
_connection.start();

_connection.on("ReceiveAnnotationSync", async function (annotationSync) {

    // set flag to avoid infinite loops
    _updating = true;

    var currentJson = TXDocumentViewer.annotations.export();

    if (currentJson != annotationSync.annotationJson)
        TXDocumentViewer.annotations.load(annotationSync.annotationJson);

    setTimeout(function () {
        _updating = false;
    }, 1000);

});