Missing element in html after specifying parent in el object: '#app'?

Question

Vue.js

I didn’t fully understand what the joke was, I indicated the parent selector in the new Vue object, after that the element in html disappeared and I see emptiness))

Answer 1

@click="pushNumbars() reader.push(*)"

It is because of such art that the template is not rendered.
There should be a semicolon between the expressions, and there are still not enough quotes - try to guess where. Well, in a good way - instead of this disgrace, it would be necessary to make a method, and the mistakes will be more obvious.

Answer 2

Press F12, there usually errors are written on the Console tab.