Is it possible to increase the variable in data inside the template?

Question

Vue.js

<template>
  <div>
    {{  (() => { count++; return count; })() }}
  </div>
</template>

<script>
  export default {
    data: function() {
      return {
        count: 0
      }
    }
  }

Answer 1

Technically possible, practically impossible. It will be updated every redraw, and in vue you have no control over the redraw, vue redraws itself when it sees fit. You can guess how many and when there will be redraws, because vue doesn't draw too much, but no guarantees.
Well, in general, the template is for display, any changes inside it are a desecration of the very idea.