google apps script code to randomize a list in a document

Code.gs

function onOpen() {
  DocumentApp.getUi()
    .createMenu('Multiple-Choice-Randomizer')
    .addItem('Run', 'randomizer')
    .addToUi();
}

function randomizer() {
  var doc = DocumentApp.getActiveDocument();
  
  var selection = doc.getSelection();
  
  var elements = selection.getRangeElements()
    .map(function(element) {
      return element.getElement().asText().getText();
    });
    
  var shuffled = shuffle(elements.slice());
  
  var selectedText = doc.getSelection().getRangeElements();
  
  for(var i = 0; i < elements.length; i++ ) {
    selectedText[i].getElement().asText().setText(shuffled[i]);
  }
}

function shuffle(a) {
  var j, x, i;
  
  for(var i = a.length; i; i--) {
    j = Math.floor(Math.random() * i);
    x = a[i - 1];
    a[i - 1] = a[j];
    a[j] = x;
  }
  
  return a;
}