Function query

06.Router/basic/js/vue.js:1124–1133

* Query an element selector if it's not an element already. * * @param {String|Element} el * @return {Element}

(el)

   */

  function query(el) {
    if (typeof el === 'string') {
      var selector = el;
      el = document.querySelector(el);
      if (!el) {
        'development' !== 'production' && warn('Cannot find element: ' + selector);
      }
    }
    return el;
  }

  /**
   * Check if a node is in the document.