title: How to update the value of an existing key of a map in Angular 4+
body: <p>Is there any way to update the value of a created key value pair map in angular 4+.</p>
  
  <p>say i have:</p>
  
  <pre><code>testMap: Map&lt;number, string&gt; = new Map&lt;number, string&gt;();
  
  ngOnInit() {
      this.testMap.set(1, "A");
      this.testMap.set(2, "B");
      this.testMap.set(3, "C");
      this.testMap.set(4, "D");
      this.testMap.set(5, "E");
  }
  
  changeValue(id){
      //id is the one of the keys of the map whose value needs to be altered
      //let say (id=3)
      this.testMap.put(id,"ChangedValue"); //PUT is from java
  }
  </code></pre>