title: How to add a key-value pair to state Object React
body: <p>I'm struggling with setting the state of one of my objects in React. The code which I have:</p>
  
  <pre><code>export class RRHN_App extends React.Component {
     constructor(props) {
        super(props);
        this.startLoadingItems();
        this.fetchData();
        this.state = {
           items: [],
           itemStatus : [],
           selectedItem: null,
           prefsDialog: false,
           preferences : {
               color : "brown",
               listSize : 800
           }
        }
     }
     toggleItem(item) {
        console.log("Selected item: ", item);
        if( this.state.selectedItem &amp;&amp;
            item.id === this.state.selectedItem.id) {
           this.setState({selectedItem: null});
        } else {
           let ItemID= item.id;
           let newSeen = {ItemID : "seen"};
           this.setState({selectedItem: item});
           this.setState({itemStatus: newSeen});
        }
        console.log(this.state.itemStatus)
     }
     fetchData() {
          request.get("http://localhost:3000/itemStatuses")
              .end( (err,response) =&gt; {
                  this.setState({itemStatus: response.body})
              })
      }
     startLoadingItems() {
          request.get("http://localhost:3000/hn/topstories")
              .end( (err,response) =&gt; {
                  this.setState({items : response.body})
              })
      }
  }
  </code></pre>
  
  <p>When printing the <code>itemStatus</code> I get this:</p>
  
  <pre><code>{16490176: "seen", 16497964: "seen", 16514428: "read", 16542395: "read", 16566536: "read"}
  </code></pre>
  
  <p>When the code is executed the <code>itemStatus</code> looks like this:</p>
  
  <pre><code>{ItemID: "seen"}
  </code></pre>
  
  <p>How can I add a key-value pair of the item.id and "seen" to the state?</p>