A documented restriction与文档和工作表插件的区别是 Apps 脚本无法判断用户在插件之外做了什么。给出了这个诱人的提示:

It is possible to poll for changes in a file's contents from a sidebar's client-side code, although you'll always have a slight delay. That technique can also alert your script to changes in the user's selected cells (in Sheets) and cursor or selection (in Docs).

遗憾的是，这在任何演示代码中都没有显示。我该怎么做？

最佳答案

轮询是通过加载项用户界面中的 html 代码完成的，使用 google.script.run 调用服务器端 Apps 脚本函数。

使用 jQuery 可以简化这一点，我们甚至可以从 jQuery, simple polling example 的答案开始.

function doPoll(){
    $.post('ajax/test.html', function(data) {
        alert(data);  // process results here
        setTimeout(doPoll,5000);
    });
}

如果我们将 ajax 调用替换为 GAS 等效项，则基本思想可以适用于 Google Apps 脚本。

这是您将在 html 文件中使用的轮询函数的框架:

  /**
   * On document load, assign click handlers to button(s), add
   * elements that should start hidden (avoids "flashing"), and
   * start polling for document updates.
   */
  $(function() {
    // assign click handler(s)

    // Add elements that should start hidden

    // Start polling for updates
    poll();
  });

  /**
   * Poll a server-side function 'serverFunction' at the given interval 
   * and update DOM elements with results. 
   *
   * @param {Number} interval   (optional) Time in ms between polls.
   *                            Default is 2s (2000ms)
   */
  function poll(interval){
    interval = interval || 2000;
    setTimeout(function(){
      google.script.run
       .withSuccessHandler(
         function(results) {
           $('#some-element').updateWith(results);
           //Setup the next poll recursively
           poll(interval);
         })
       .withFailureHandler(
         function(msg, element) {
           showError(msg, $('#button-bar'));
           element.disabled = false;
         })
       .serverFunction();
    }, interval);
  };

附加示例，文档轮询器

这是调用服务器端 Google Apps 脚本函数以检测 Google 文档中的用户行为的 jQuery 轮询技术的演示。它没有做任何有用的事情，但它展示了一些通常需要了解用户的事件和文档状态的事情，例如对按钮的上下文敏感控制。

同样的原则也适用于电子表格或独立的 GAS Web 应用程序。

喜欢this question中的UI App示例，此技术可用于绕过执行时间限制，至少对于具有用户界面的操作。

该代码基于来自 Google 5-minute quickstart 的示例插件.按照该指南中的说明进行操作，使用下面的代码而不是快速入门中的代码。

代码.gs

/**
 * Creates a menu entry in the Google Docs UI when the document is opened.
 *
 * @param {object} e The event parameter for a simple onOpen trigger. To
 *     determine which authorization mode (ScriptApp.AuthMode) the trigger is
 *     running in, inspect e.authMode.
 */
function onOpen(e) {
  DocumentApp.getUi().createAddonMenu()
      .addItem('Start', 'showSidebar')
      .addToUi();
}

/**
 * Runs when the add-on is installed.
 *
 * @param {object} e The event parameter for a simple onInstall trigger. To
 *     determine which authorization mode (ScriptApp.AuthMode) the trigger is
 *     running in, inspect e.authMode. (In practice, onInstall triggers always
 *     run in AuthMode.FULL, but onOpen triggers may be AuthMode.LIMITED or
 *     AuthMode.NONE.)
 */
function onInstall(e) {
  onOpen(e);
}

/**
 * Opens a sidebar in the document containing the add-on's user interface.
 */
function showSidebar() {
  var ui = HtmlService.createHtmlOutputFromFile('Sidebar')
      .setTitle('Document Poller');
  DocumentApp.getUi().showSidebar(ui);
}

/**
 * Check if there is a current text selection.
 *
 * @return {boolean}  'true' if any document text is selected
 */
function checkSelection() {
  return {isSelection : !!(DocumentApp.getActiveDocument().getSelection()),
          cursorWord : getCursorWord()};
}

/**
 * Gets the text the user has selected. If there is no selection,
 * this function displays an error message.
 *
 * @return {Array.<string>} The selected text.
 */
function getSelectedText() {
  var selection = DocumentApp.getActiveDocument().getSelection();
  if (selection) {
    var text = [];
    var elements = selection.getSelectedElements();
    for (var i = 0; i < elements.length; i++) {
      if (elements[i].isPartial()) {
        var element = elements[i].getElement().asText();
        var startIndex = elements[i].getStartOffset();
        var endIndex = elements[i].getEndOffsetInclusive();

        text.push(element.getText().substring(startIndex, endIndex + 1));
      } else {
        var element = elements[i].getElement();
        // Only translate elements that can be edited as text; skip images and
        // other non-text elements.
        if (element.editAsText) {
          var elementText = element.asText().getText();
          // This check is necessary to exclude images, which return a blank
          // text element.
          if (elementText != '') {
            text.push(elementText);
          }
        }
      }
    }
    if (text.length == 0) {
      throw 'Please select some text.';
    }
    return text;
  } else {
    throw 'Please select some text.';
  }
}

/**
 * Returns the word at the current cursor location in the document.
 *
 * @return {string}   The word at cursor location.
 */
function getCursorWord() {
  var cursor = DocumentApp.getActiveDocument().getCursor();
  var word = "<selection>";
  if (cursor) {
    var offset = cursor.getSurroundingTextOffset();
    var text = cursor.getSurroundingText().getText();
    word = getWordAt(text,offset);
    if (word == "") word = "<whitespace>";
  }
  return word;
}

/**
 * Returns the word at the index 'pos' in 'str'.
 * From https://stackoverflow.com/questions/5173316/finding-the-word-at-a-position-in-javascript/5174867#5174867
 */
function getWordAt(str, pos) {

  // Perform type conversions.
  str = String(str);
  pos = Number(pos) >>> 0;

  // Search for the word's beginning and end.
  var left = str.slice(0, pos + 1).search(/\S+$/),
      right = str.slice(pos).search(/\s/);

  // The last word in the string is a special case.
  if (right < 0) {
    return str.slice(left);
  }

  // Return the word, using the located bounds to extract it from the string.
  return str.slice(left, right + pos);
}

边栏.html

<link rel="stylesheet" href="https://ssl.gstatic.com/docs/script/css/add-ons.css">
<!-- The CSS package above applies Google styling to buttons and other elements. -->


<div class="sidebar branding-below">
  <form>
    <div class="block" id="button-bar">
      <button class="blue" id="get-selection" disabled="disable">Get selection</button>
    </div>
  </form>
</div>

<div class="sidebar bottom">
  <img alt="Add-on logo" class="logo" height="27"
      id="logo"
      src="https://www.gravatar.com/avatar/adad1d8ad010a76a83574b1fff4caa46?s=128&d=identicon&r=PG">
  <span class="gray branding-text">by Mogsdad, D.Bingham</span>
</div>

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">
</script>
<script>
  /**
   * On document load, assign click handlers to button(s), add
   * elements that should start hidden (avoids "flashing"), and
   * start polling for document selections.
   */
  $(function() {
    // assign click handler(s)
    $('#get-selection').click(getSelection);


    // Add elements that should start hidden
    var newdiv1 = $( "<div class='block' id='cursor-word'/>" ).hide(),
        newdiv2 = $( "<div class='block' id='selected-text'/>" ).hide();
    $('#button-bar').after( newdiv1, newdiv2 );
    $('#cursor-word').html('<H2>Word at cursor:</H2><p id="cursor-word-content"></p>');
    $('#selected-text').html('<H2>Selected text:</H2><p id="selected-text-content"></p>');

    // Start polling for updates        
    poll();
  });

  /**
   * Poll the server-side 'checkSelection' function at the given
   * interval for document selection, and enable or disable the
   * '#get-selection' button.
   *
   * @param {Number} interval   (optional) Time in ms between polls.
   *                            Default is 2s (2000ms)
   */
  function poll(interval){
    interval = interval || 2000;
    setTimeout(function(){
      google.script.run
       .withSuccessHandler(
         function(cursor) {
           if (cursor.isSelection) {
             // Text has been selected: enable button, hide cursor word.
             $('#get-selection').attr('disabled', false);
             $('#cursor-word').hide();
             // $('#selected-text').show();  // Not so fast - wait until button is clicked.
           }
           else {
             $('#get-selection').attr('disabled', true);
             $('#cursor-word').show();
             $('#selected-text').hide();
           }
           $('#cursor-word-content').text(cursor.cursorWord);
           //Setup the next poll recursively
           poll(interval);
         })
       .withFailureHandler(
         function(msg, element) {
           showError(msg, $('#button-bar'));
           element.disabled = false;
         })
       .checkSelection();
    }, interval);
  };

  /**
   * Runs a server-side function to retrieve the currently
   * selected text.
   */
  function getSelection() {
    this.disabled = true;
    $('#error').remove();
    google.script.run
      .withSuccessHandler(
        function(selectedText, element) {
          // Show selected text
          $('#selected-text-content').text(selectedText);
          $('#selected-text').show();
          element.disabled = false;
        })
      .withFailureHandler(
        function(msg, element) {
          showError(msg, $('#button-bar'));
          element.disabled = false;
        })
      .withUserObject(this)
      .getSelectedText();
  }


  /**
   * Inserts a div that contains an error message after a given element.
   *
   * @param msg The error message to display.
   * @param element The element after which to display the error.
   */
  function showError(msg, element) {
    var div = $('<div id="error" class="error">' + msg + '</div>');
    $(element).after(div);
  }
</script>

轮询间隔

setTimeout() 函数接受以毫秒表示的时间间隔，但我通过实验发现，两秒的响应是可以预期的最佳响应。因此，骨架 poll() 的默认间隔为 2000 毫秒。如果您的情况可以容忍轮询周期之间更长的延迟，则通过对 poll() 的 onLoad 调用提供更大的值，例如poll(10000) 一个 10 秒的轮询周期。

工作表

有关工作表示例，请参阅 How do I make a Sidebar display values from cells?

关于javascript - 如何从附加组件中轮询 Google 文档，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24773177/