title: How should Vue filters be bound using typescript?
body: <p>How should Vue filters be bound using TypeScript? It is fairly straightforward with pure js, but I'm running into issue converting it to TypeScript.</p>
  <p>The code and compile error are as follows:</p>
  <p><strong>app.ts</strong></p>
  <pre><code>import * as Vue from 'vue'
  ...
  import * as filters from './util/filters'
  
  // register global utility filters.
  Object.keys(filters).forEach(key =&gt; {
    Vue.filter(key, filters[key]);
  })
  </code></pre>
  <p><strong>util/filters.ts</strong></p>
  <pre><code>export function host (url: string) {
    ...
  }
  
  export function timeAgo (time: any) {
    ....
  }
  </code></pre>
  <p><strong>Compile Error</strong></p>
  <p><em>error TS7017: Element implicitly has an 'any' type because type 'typeof ...' has no index signature.</em></p>