conditional Vue initialization to accommodate for Experience Editor

InitializeVueEE.js

// check if this is Experience Editor
if (typeof Sitecore !== typeof undefined && 
    typeof Sitecore.PageModes !== typeof undefined && 
    typeof Sitecore.PageModes.PageEditor !== typeof undefined) {
  Sitecore.PageModes.PageEditor.onLoadComplete.observe(() => {
    // add v-pre to all placeholder elements
    document
      .querySelectorAll("code[type='text/sitecore']")
      .forEach(ph => ph.setAttribute('v-pre', ''));

    // then initialize Vue
    new Vue({
      el: '#app'
    });
  });
} else {
  // initialize Vue directly if not in EE
  new Vue({
    el: '#app'
  });
}