var number = 1;
    document.write('<table>');
    for (var i = 0; i < 4; i++) {
      document.write('<tr>');
      for (var j = 0; j < 4; j++) {
        document.write('<td id="'+number+'"></td>');
        number++;
      }
      document.write('<td class="button" onclick="switchLightRow('+(number-1)+')"></td>');
      document.write('</tr>');
    }
    document.write('<tr>');
    for (var k = 0; k < 4; k++) {
      document.write('<td class="button" onclick="switchLightColumn('+(k+1)+')"></td>');
    }
    document.write('</tr>');
    document.write('</table>');


    function switchLightRow(num) {
      for (var i = 0; i < 4; i++) {
          numcase = num - i;
          if (document.getElementById(numcase).style.backgroundColor == 'white') {

            document.getElementById(numcase).style.backgroundColor = "yellow";

          }else {
            document.getElementById(numcase).style.backgroundColor = "white";
          }
      }
      td = document.getElementsByTagName('td');
      var lightIsOn = 0;
      for (var i = 0; i < td.length; i++) {
        if(td[i].style.backgroundColor == "yellow"){
          lightIsOn++;
        }
      }
      console.log(lightIsOn);
      if (lightIsOn == 16) {
        document.write('Félicitations !')
      }
      var lightIsOn = 0;

    }

    function switchLightColumn(num){
      for (var i = 0; i < 4; i++) {
        numcase = num + i * 4;
        if (document.getElementById(numcase).style.backgroundColor == 'white') {

          document.getElementById(numcase).style.backgroundColor = "yellow";

        }else {
          document.getElementById(numcase).style.backgroundColor = "white";
        }
      }
      td = document.getElementsByTagName('td');
      var lightIsOn = 0;
      for (var i = 0; i < td.length; i++) {
        if(td[i].style.backgroundColor == "yellow"){
          lightIsOn++;
        }
      }
      console.log(lightIsOn);
      if (lightIsOn == 16) {
        document.write('Félicitations !')
      }
      var lightIsOn = 0;
    }