Automate Paragraph Transformations in Google Docs with Google Apps Script

function convertExercisesToHeadings() {
  const doc = DocumentApp.getActiveDocument();
  const body = doc.getBody();
  const paragraphs = body.getParagraphs();

  const exercisePattern = /^\/\/\s*Exercise\s*\d+\s*:/;

  paragraphs.forEach(paragraph => {
    const text = paragraph.getText();
    if (exercisePattern.test(text)) {
      const newText = text.replace(exercisePattern, '').trim();
      paragraph.setText(newText);
      paragraph.setHeading(DocumentApp.ParagraphHeading.HEADING3);
    }
  });
}