How to Update Text Boxes in Google Slides Using Google Apps Script

function updateTextBoxes() {
  var presentation = SlidesApp.getActivePresentation();
  var slides = presentation.getSlides();
  
  slides.forEach(function(slide, index) {
    var shapes = slide.getShapes();
    shapes.forEach(function(shape) {
      if (shape.getShapeType() === SlidesApp.ShapeType.TEXT_BOX) {
        // Accessing the text range of the text box
        var textRange = shape.getText();
        // Clear existing text
        textRange.clear();
        // Set new text content
        textRange.setText('New text content for slide ' + (index + 1));
      }
    });
  });
}