title: Initialize a Map containing arrays in TypeScript
body: <p>I want to make a <code>Map</code> where each member contains an array of strings. But how do I initialize and type it (in a single statement)?</p>
  <p>(naively) I tried this:</p>
  <pre><code>  private _gridOptions:Map&lt;string, Array&lt;string&gt;&gt; = {&quot;1&quot;: [&quot;test&quot;]};
  </code></pre>
  <p>and I get:</p>
  <pre><code>Module build failed: Error: /Users/*****/Work/dashboard/src/app/core/pg.service.ts (8,5): Type '{ &quot;1&quot;: string[]; }' is not assignable to type 'Map&lt;string, string[]&gt;'.
  </code></pre>