An interesting Stack Overflow question popped up about auto-translating one document into another when edits are made. Most Google services have things called “triggers” which run functions after some kind of event – opening the doc, making a change, etc.

A Google Doc does not have access to the onEdit trigger, so there is no way to automatically run the translation unless you put it on a timer trigger, and that’s a waste of resources, especially if you’re not constantly updating the document. But, you can link two documents together via the ID and push changes made using a custom menu.

Grab a copy of the template with instructions.

Source:

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

function getText() {
  var doc = DocumentApp.getActiveDocument();
  var body = doc.getBody();
  var array = [];

  array.push(body.getText());

  sendTheText(array);
}

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);
  }
  var childDoc = DocumentApp.openById(docProps.getProperty("childId"));
  var es = LanguageApp.translate(e, 'en', 'es');
  childDoc.getBody().clear();
  childDoc.getBody().appendParagraph(es);
}

function clearProps() {
  docProps.setProperty("childId", "");
}

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