Automation of numbering Heading 2 titles using Google Apps Script in Google Docs

Here’s a Google Apps Script that scans a Google Doc, finds all Heading 2 paragraphs, and adds sequential numbering before each heading.

Apps Script Code

function numberHeading2InDoc() {
  var doc = DocumentApp.getActiveDocument();
  var body = doc.getBody();
  var paragraphs = body.getParagraphs();
  var count = 1; // Start numbering from 1
  
  for (var i = 0; i < paragraphs.length; i++) {
    var paragraph = paragraphs[i];

    // Check if the paragraph is Heading 2
    if (paragraph.getHeading() === DocumentApp.ParagraphHeading.HEADING2) {
      var text = paragraph.getText().trim();

      // Check if the heading is already numbered to prevent duplicate numbering
      if (!/^\d+\.\s/.test(text)) {
        paragraph.setText(count + ". " + text);
        count++; // Increment the counter
      }
    }
  }
}

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How the Script Works

1. Accesses the Current Document:
   • Retrieves the active Google Doc.
2. Loops Through All Paragraphs:
   • Scans each paragraph in the document.
3. Finds Heading 2 Text:
   • Uses paragraph.getHeading() to identify paragraphs styled as Heading 2.
4. Adds Sequential Numbering:
   • Starts numbering from 1 and increases for each new Heading 2.
   • Ensures that it doesn’t double-number headings by checking if they are already numbered.

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Example Before and After

Before Running Script	After Running Script
Introduction	1. Introduction
Getting Started	2. Getting Started
Advanced Features	3. Advanced Features

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How to Use This Script

Step 1: Open Google Apps Script

1. Open your Google Doc.
2. Click on Extensions > Apps Script.

Step 2: Add the Script

1. Delete any existing code in the editor.
2. Copy and paste the script above.

Step 3: Run the Script

1. Click the Run button (▶) in the Apps Script editor.
2. If prompted, grant permissions to allow the script to modify the document.

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Why This is Useful

✅ Automatic Numbering: No need to manually number headings.
✅ Prevents Duplicate Numbers: Avoids adding numbers if they already exist.
✅ Perfect for Reports & Outlines: Helps structure documents with clear numbering.