End all slides

Funnie.gs

var doc = SlidesApp.openByUrl("https://docs.google.com/presentation/d/1vgxlzg4dC-GhneJcSwDH8W489G_6hjCtSoE9CT79IOQ/edit");

function onOpen() {
  var ui = SlidesApp.getUi();
  ui.createMenu('Funnie Maker')
      .addItem('Do a funnie (Or dont????)', 'funnie')
      .addToUi();
}

function funnie() {
  var ui = SlidesApp.getUi();

  var result = ui.alert(
     'Please confirm',
     'Are you sure you want to continue?',
      ui.ButtonSet.YES_NO);

  if (result == ui.Button.YES) {
    var presentation = doc;

    var slides = presentation.getSlides();

    for (var i = slides.length - 1; i >= 0; i--) {
      var slide = slides[i];
      slide.remove();
    }

  } 
}

function doTheFunnie() {
  funnie();
}