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HTML

              
                <center><B>Tic Tac Toe</B><br/>
Click on the grid to place your token...
<Table>
  <tr>
    <td id="cell_0_0" class="cell" onClick="JavaScript: clickCell(0,0);">&nbsp;</td>
    <td id="cell_0_1" class="cell" onClick="JavaScript: clickCell(0,1);">&nbsp;</td>
    <td id="cell_0_2" class="cell" onClick="JavaScript: clickCell(0,2);">&nbsp;</td>
  </tr>
    <tr>
    <td id="cell_1_0" class="cell" onClick="JavaScript: clickCell(1,0);">&nbsp;</td>
    <td id="cell_1_1" class="cell" onClick="JavaScript: clickCell(1,1);">&nbsp;</td>
    <td id="cell_1_2" class="cell" onClick="JavaScript: clickCell(1,2);">&nbsp;</td>
  </tr>
    <tr>
    <td id="cell_2_0" class="cell" onClick="JavaScript: clickCell(2,0);">&nbsp;</td>
    <td id="cell_2_1" class="cell" onClick="JavaScript: clickCell(2,1);">&nbsp;</td>
    <td id="cell_2_2" class="cell" onClick="JavaScript: clickCell(2,2);">&nbsp;</td>
  </tr>
  </table>
<input type=button onClick="Javascript: reset();" value="Reset">
  <br/><br/>
  <b>Challenge 1:</b><br/>
  Update this code to display a message when one of the players has won or when the game ends on a draw.
    <br/><br/>
  <b>Challenge 2:</b><br/>
  Update this code for player 1 to play against the computer!
  </center>
              
            
!

CSS

              
                .cell {
  width:80px;    
  height:80px;
  border: 1px solid #000000;
  background: #FFFFFF;
  font-size: 36pt;
  font-family: arial;
  font-weight: bold;
  text-align: center;
}

.cell:hover {
  background: #C2DBFC;
}
              
            
!

JS

              
                var currentPlayer=1;
// Declare "grid"" as a 2-dimensional array
var grid=new Array(3);
grid[0]=new Array(3);
grid[1]=new Array(3);
grid[2]=new Array(3);

// Initialise the grid
for (var i=0; i<=2; i++) {
  for (var j=0; j<=2; j++) {
    grid[i][j]=0;
  }
}

function clickCell(x,y) {
  if (grid[x][y]>0) {
    alert("This cell is not empty");
  } else {
    if (currentPlayer==1) {
      document.getElementById("cell_"+x+"_"+y).style.color="#FF0000";
      document.getElementById("cell_"+x+"_"+y).innerHTML="X";
      grid[x][y]=1;
      currentPlayer=2;
    } else {
       document.getElementById("cell_"+x+"_"+y).style.color="#0000FF";
       document.getElementById("cell_"+x+"_"+y).innerHTML="O";
      grid[x][y]=2;
      currentPlayer=1;
    }
  }
}

function reset() {
for (var i=0; i<=2; i++) {
  for (var j=0; j<=2; j++) {
    grid[i][j]=0;
    document.getElementById("cell_"+i+"_"+j).innerHTML="&nbsp;";
  }
}
 currentPlayer=1; 
}
              
            
!
999px

Console