title: Angular rxjs : The List Object map method is not consistency?
body: <p>I don't know why my code is returning unexpected output, I assume I am not familiar with the logic how to use map method. The map return confirms and schedules separately. I would like to get the result as below, but it output empty list twice. sometime the first one is empty, the example below I gave is the other result. Any help will be much appreciated!</p>
  <p>This is a typescript code using rxjs map if i understand right.</p>
  <p>Code here:</p>
  <pre><code>const confirms = this.List.map(r =&gt; {
            console.log('confirmed',r.map(c =&gt; c.ConfirmedCapacity));
            return r.map(c =&gt; c.ConfirmedCapacity)[etaIndex];
          });
  
  const schedules = this.List.map(r =&gt; {
            console.log('scheduled',r.map(c =&gt; c.ConfirmedCapacity));
                return r.map(c =&gt; c.ScheduledCapacity)[etaIndex];
          });
  </code></pre>
  <p>Expected result:</p>
  <pre><code>confirmed (21) [0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  scheduled (21) [0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  </code></pre>
  <p>Get :</p>
  <pre><code>confirmed (21) [0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  confirmed (21) [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  scheduled (21) [0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  scheduled (21) [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  </code></pre>