title: How to map json object to array
body: <p>I have json:</p>
  
  <pre><code>{
    "userList":
    [{
      "name": "Bob",
      "age": 28
    },{
      "name": "Tom",
      "age": 45
    },{
      "name": "Alice",
      "age": 32
    }]
  }
  </code></pre>
  
  <p>I want to cut only age and put them to array like : public mainChartData1: Array = [28, 45, 32];</p>
  
  <p>I have started to do that by next code:</p>
  
  <pre><code>  const arr = this.users.map(obj =&gt; {
  
      var localObj = [];
        localObj[obj] = obj.age;
        return localObj;
  
      });
  </code></pre>
  
  <p>But it doesn't work.</p>