Updated toggle button feature

src/BoardSwitcher.js

@@ -15,19 +15,32 @@ class Board extends React.Component {
 }
 
 class BoardSwitcher extends React.Component {
+  constructor(props){
+    super(props);
+    this.state = {
+      spot: 0,
+    };
+  }
+
+  handleClick(event){
+    this.setState({
+      spot: (this.state.spot+1)%3
+    })
+  }
+
   render() {
-    let boards = [];
-    for (let ii = 0; ii < this.props.numBoards; ii++) {
-      let isSelected = ii === 0;
+    let boards = [];  // empty array of boards
+    for (let ii = 0; ii < this.props.numBoards; ii++) { // fill the array with n(param) boards
+      let isSelected = ii === this.state.spot;  // let the first one be selected
       boards.push(
-        <Board index={ii} selected={isSelected} key={ii} />
+        <Board index={ii} selected={isSelected} key={ii} /> // returns a 'Board' object with those params
       );
     }
 
     return (
       <div>
         <div className="boards">{boards}</div>
-        <button>Toggle</button>
+        <button onClick={ (e) => this.handleClick(e) }>Toggle</button>
       </div>
     );
   }