title: RxJS reduce function value param return whole arr instead of normal reduce function do
body: <p>I am developing Angular app right now, and wanna call a service that return Array of Users (Assumed)</p>
  
  <p>The response of the service is like</p>
  
  <pre><code>[{id: 1, name: 'foo'}, 
   {id: 2, name: 'bar'}]
  </code></pre>
  
  <p>I want to calculate each item based on previous object, so I come out to use REDUCE function to replace all the objects in the array, and the ITEM object just return all the array to me instead of one, so I try return last item to inspect the result like this.</p>
  
  <pre><code>of(users).pipe(
    reduce((arr, item)=&gt;item, [])
  ).subscribe(r=&gt;console.log(r))
  // [{id: 1, name: 'foo'}, {id: 2, name: 'bar'}]
  </code></pre>
  
  <p>But I try to use normal reduce function, it returns</p>
  
  <pre><code>users.reduce((arr, item)=&gt;item), [])
  // {id: 2, name: 'bar'}
  </code></pre>
  
  <p>Here is my example on stackblitz <a href="https://stackblitz.com/edit/rxjs-e97p4c?devtoolsheight=60" rel="nofollow noreferrer">https://stackblitz.com/edit/rxjs-e97p4c?devtoolsheight=60</a></p>