Type checking without Typescript

[laspinacristian]

With Vetur I can get proper type checking in VScode using just Javascript (with JSDoc comments where necessary) and putting a jsconfig.json on root folder of my project with "checkJs": true

Is this possibile with Volar?
I tried and it seems that type checking are enable only when lang="ts" on <script> is present

[johnsoncodehk]

It's supports. allowJs + checkJs combo works for me in https://github.com/johnsoncodehk/volar-starter.

If it don't works for you, please provide a repro case.

[laspinacristian]

Hi @johnsoncodehk,

I meant it will not do type checking inside template interpolations (sorry to have not specified this)
In your example if you do

<template>
<p>{{ count.toLowerCase() }}</p>
</template>

count.toLowerCase() won't be highlited as error.

[johnsoncodehk]

@laspinacristian we can't support template type-check in js with defineComponent, because typescript only performs limited type calculations on js code, the type calculation of defineComponent is too complicated, so defineComponent callback type is always any in js.

// test.js
const Comp = (await import('vue')).defineComponent({ setup() { return { count: 0 } } });
(new Comp()).count.toLowerCase // no error

// test.ts
const Comp = (await import('vue')).defineComponent({ setup() { return { count: 0 } } });
(new Comp()).count.toLowerCase // Property 'toLowerCase' does not exist on type 'number'.ts(2339)