title: Typescript map.get return undefined
body: <p>When I want get <code>Object</code> by <code>key</code> I have <code>undefined</code> each all element.</p>
  
  <p>My Map : </p>
  
  <pre><code>nodesMaps : Map&lt;number, Object&gt; = [
  { key: "1", value: Object },
  { key: "2", value: Object },
  { key: "3", value: Object },
  ]
  </code></pre>
  
  <p>When I want get value of this map :</p>
  
  <pre><code>this.nodesMaps.get(1) // return undefined
  this.nodesMaps.get("1") // return undefined
  </code></pre>