title: Vue type script - data and custom types
body: <p>I have a type called student.</p>
  <pre><code>export interface Student {
    name: string,
    age: number
  }
  </code></pre>
  <p>I want to assign that type to data to a student.</p>
  <pre><code>data() {
  const tommy: Student = {}
  return {
    tommy,
  </code></pre>
  <p>}</p>
  <p>However when I assign a string to that data in the mounted hook  I get no warnings or issues.</p>
  <pre><code>  async mounted() {
      this.tommy= 'Tommy Smith'
  </code></pre>
  <p>How should I define custom data types in vue typescript.</p>