Tic Tac Toe issue with computer AI

I'm trying to make this freeCodeCamp challenge.. i have a problem with my computer AI

a little explanation--

every time is computer turn i push every item of my array disponibili (available ) in a mossa_calcolata array.. then i cancat this with computer_ moves array and i get my comp_possible array..the same things is done for player1;

after this i use my checkwin function with my comp_possible and if its true i use my disegnaSegno() function for put the moves in the right place...but if checkWin its not true i check the player possibilities...

but the problem is:sometimes computer prefer to block the players winning move insted of closing the game..especially if player1 start the game..

else if (computer_moves.length >= 1 && player1_moves.length >= 1) {

dance: for (var j = 1; j < disponibili.length; j++) {

    mossa_calcolata = [];
    comp_possible = [];
    player_possible = [];

    mossa_calcolata.push(disponibili[j]);
    comp_possible = computer_moves.concat(mossa_calcolata);
    player_possible = player1_moves.concat(mossa_calcolata);

    for (var x = 0; x < possible_wins.length; x++) {


      if (checkWin(comp_possible, possible_wins[x])) {

        console.log("primo caso");
        console.log(possible_wins[x]);

        disegnaSegno(disponibili[j]);
        svuotaDisponibili(disponibili[j]);
        computer_moves.push(disponibili[j]);

        setTimeout(function() {
          segnalaVittoria(possible_wins[x]);
        }, 1500);

        setTimeout(function() {
          popUpVittoria("computer");
        }, 2000);

        player2_counter++;
        $("#player2-counter").text(player2_counter);

        //break dance;

      } else if (checkWin(player_possible, possible_wins[x])) {

        console.log("secondo caso");
        console.log(possible_wins[x]);
        disegnaSegno(disponibili[j]);
        computer_moves.push(disponibili[j]);
        svuotaDisponibili(disponibili[j]);

        break dance;

      } 
    }
  }
}

this is my codepen link for complete code http://ift.tt/2mWNNQI