2339: Property '...' does not exist on type 'CombinedVueInstance<Vue, object, object, object, Record<never, any>>'.

Just assign a functional property.

<script>
export default {
  functional: false,  // or true
  ...
}
</script>

I'm writing Vue.js in JavaScript not in TypeScript. This error message might be for TypeScript.

But the error message appear in my editor vim with ale. And I still cannot find out which module gives me this message.

2339: Property 'category' does not exist on type 'CombinedVueInstance<Vue, object, object, object, Record<never, any>>'.

Anyway, luckily, I found this temporary solution.