How to solve the error "Property "count" was accessed during render but is not defined on instance. at"?

Question

JavaScript

Hi, I just started learning Vue.js and ran into a bug. Property "count" was accessed during render but is not defined on instance. at. At the same time, neither counter nor title is displayed on the page. Screenshots of 3 files:

Answer 1

export default {
  data() {
    return ...