The `undefined` kind of issue

something.js

/*
  Return the same of `.get(index)` method,
  but if the return of `.get` is undefined
  this method will return an empty array `[]`
  and NOT an `undefined`
  
  Useful to make sure things wont break if
  an element isn't in the DOM
*/
var getThat = function (index) {
  return this.get(index) || []
}

jQuery.fn.extend({
  getThat: getThat
});

/*
  So...
*/

jQuery('.not-in-dom').getThat(0).innerHTML = 'Hi'; // It doesn't throw error
// but
jQuery('.not-in-dom').get(0).innerHTML = 'Hi'; // Throw can't read `innerHTML` from `undefined`