Link two documents for translation updates

linkTranslatedDocs.gs

var ui = DocumentApp.getUi();
var docProps = PropertiesService.getDocumentProperties();

// Grab the document body.
// No formatting, tables, etc are kept.
function getText() {
  var doc = DocumentApp.getActiveDocument();
  var body = doc.getBody();
  Logger.log(body.getText());
  var array = [];
  array.push(body.getText());
  sendTheText(array);
}

// Check for a Doc ID to push to. If none, ask for it.
// Push the doc and translate to Spanish.
function sendTheText(e) {
  if (docProps.getProperty("childId") == "") {
    var prompt = ui.prompt("Child doc ID", ui.ButtonSet.OK);
    var response = prompt.getResponseText()
    docProps.setProperty("childId", response);
    Logger.log(response);
  }
  var childDoc = DocumentApp.openById(docProps.getProperty("childId"));
  var es = LanguageApp.translate(e, 'en', 'es');
  childDoc.getBody().clear();
  childDoc.getBody().appendParagraph(es);
}

// Reset the doc you're pushing updates to
function clearProps() {
  docProps.setProperty("childId", "");
}

function onOpen() {
  ui.createMenu("Custom Translate").addItem("Run", "getText").addItem("Clear IDs","clearProps").addToUi();
}