tx.js

async function saveDocument(StreamType) {
    
    // save document
    return new Promise((resolve, reject) => {
        TXTextControl.saveDocument(StreamType, function (e) {
            if (e) {
                resolve(e.data);
            } else {
                reject('Error saving document');
            }
        });
    });
    
}

function loadDocumentFromUrl(url) {

    // download document using xml http request
    var xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);
    xhr.responseType = 'blob';
    xhr.onload = function () {
        if (xhr.status === 200) {
            var blob = xhr.response;
            var reader = new FileReader();
            reader.onload = function () {
                // get the base64 encoded string
                var base64 = reader.result.split(',')[1];
                // load the document
                TXTextControl.loadDocument(TXTextControl.StreamType.InternalUnicodeFormat, base64);
            };
            reader.readAsDataURL(blob);
        }
    };
    xhr.send();  
    
}