Number the Headings in Google Docs using Google App Script

Sarmad Gardezi

Is it possible to number the headings in a Google Docs/Drive document? Yes you can automatically place the numbers in heading in Google Docs using Google App Scripts.

I modified the script mentioned by Mikko Ohtamaa and created a Google Apps Script that adds a Headings tools Document menu that allows you to:

  • auto number Heading
  • clear Headings numbers

How to auto number Google Documents Headings:

  1. Open your document > Tools > Script editor…
  2. Start a blank project
  3. Paste the the code below and save with your preffered name
  4. Select Run > onOpen and authorize the script for the first time
  5. Select Run > onOpen
  6. Change to your Document and try the functions on the Headings tools custom menu created.

~~Disclaimer: you may have issues with empty Headings.. But you can always fix them and run action again.~~

Code to copy and paste:

function onOpen() {
  DocumentApp.getUi().createMenu('Headings Tools')
  .addItem('Auto Number Headings', 'numberHeadingsAdd')
  .addItem('Clear Heading Numbers', 'numberHeadingsClear')
  .addToUi();
}

function numberHeadingsAdd(){
  numberHeadings(true);
}

function numberHeadingsClear(){
  numberHeadings(false);
}

function numberHeadings(add){
  var document = DocumentApp.getActiveDocument();
  var body = document.getBody();
  var paragraphs = document.getParagraphs();
  var numbers = [0,0,0,0,0,0,0];
  for (var i in paragraphs) {
    var element = paragraphs[i];
    var text = element.getText()+'';
    var type = element.getHeading()+'';

    // exclude everything but headings
    if (!type.match(/Heading \d/)) {
      continue;
    }

    // exclude empty headings (e.g. page breaks generate these)
    if( text.match(/^\s*$/)){
      continue;
    }

    if (add == true) {
      var level = new RegExp(/Heading (\d)/).exec(type)[1];  
      var numbering = '';

      numbers[level]++;
      for (var currentLevel = 1; currentLevel <= 6; currentLevel++) {
        if (currentLevel <= level) {
          numbering += numbers[currentLevel] + '.';
        } else {
          numbers[currentLevel] = 0;
        }
      }
      Logger.log(text);
      var newText = numbering + ' ' + text.replace(/^[0-9\.\s]+/, '');
      element.setText(newText);
      Logger.log([newText]);
    } else {
      Logger.log(text);
      element.setText(text.replace(/^[0-9\.\s]+/, ''));
    }
  }

}

If you copy and paste any item of numbered list, then it retains its numbering, and automatically changes the number in relevant cases.

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