Firebase中的多人石头剪刀布，范围问题

Question

我正在火力基地开发一款剪刀石头布游戏，该游戏允许两名玩家互相对抗。我在这里TypeError: Cannot read property 'p1throw' of null到处出现错误，似乎Firebase侦听器正在运行，并且在某些情况下，结果变量没有完全删除，并且代码的某些部分正在多次运行。

我尝试了大量的控制台日志来找出问题，但是有时代码运行得很好，然后其他时候它将拉出错误。

//
// GAME MECHANICS
//


// Function to increase move count
function progressMove(num) {
  database
    .ref("/moves")
    .child("/move")
    .set(num);
}

//Listener for when move variable changes
database.ref("/moves").on("value", function(snap) {
  console.log("Move just changed to " + snap.val().move);
  if (snap.val().move === 1) {
    playerOneThrow(snap.val().move);
  }
  if (snap.val().move === 2) {
    playerTwoThrow(snap.val().move);
  }
  if (snap.val().move === 3) {
      console.log("Move is 3, evaluating match")
    evaluateMatch();
    database.ref("/results/gameresult").remove()
    console.log("removed the results node")
  }
});

function playerOneThrow() {
  $(".details").text("Player 1, choose your throw");
  $(".p1-hands").on("click", playerOneChooseHand);
}

function playerOneChooseHand() {
  $(".p1-hands").off()
  let hand = $(this).attr("data-value");
  console.log("Player 1 chose" + hand);
  progressMove(2);
  database.ref("/throws/p1throw").child("/throwVal").set(hand);
}

function playerTwoThrow() {
  $(".details").text("Player 1 has thrown, player 2, choose your throw");
  $(".p2-hands").on("click", playerTwoChooseHand);
}

function playerTwoChooseHand() {
  $(".p2-hands").off()
  progressMove(3);
  console.log("Player 2 hand clicked");
  let hand = $(this).attr("data-value");
  console.log("Player 2 chose" + hand);
  database.ref("/throws/p2throw").child("/throwVal").set(hand);
}

function evaluateMatch() {
    database.ref("/throws/")
    .once("value")
    .then(function(throwsnap) {
        console.log("Displaying throws node once for match evaluation")
        console.log(throwsnap.val())
            let p1throw = throwsnap.val().p1throw.throwVal;
            let p2throw = throwsnap.val().p2throw.throwVal;
            if (p1throw === p2throw){
                database.ref('/results/gameresult').child("/outcome").set("tie")
            } else if(p1throw === "rock"){
                if(p2throw === "paper"){
                database.ref('/results/gameresult').child("/outcome").set("p2 wins")
                } else if(p2throw === "scissors")
                database.ref('/results/gameresult').child("/outcome").set("p1 wins")
            } else if (p1throw === "paper"){
                if(p2throw === "rock"){
                database.ref('/results/gameresult').child("/outcome").set("p1 wins")
                } else if (p2throw === "scissors"){
                database.ref('/results/gameresult').child("/outcome").set("p2 wins")
                }
            } else if(p1throw === "scissors"){
                if(p2throw === "paper"){
                database.ref('/results/gameresult').child("/outcome").set("p1 wins")
                } else if (p2throw === "rock"){
                 database.ref('/results/gameresult').child("/outcome").set("p2 wins")
                }
            }
        });
    }

// Listens for change in results, triggered by setting outcome and results above
database.ref('/results/gameresult').on("child_added",function(resultsnap){
    console.log("Displaying results node because a child was added", resultsnap.val())
    database.ref("/throws/").once("value").then(function(throwsnap) {
          console.log("Displaying the throws node just once since a child was added to the game results node")
        console.log(throwsnap.val()) 
          if(resultsnap.val() === "tie"){
              ties++
          } else if (resultsnap.val() === "p1 wins"){
              p1wins++
              p2losses++
          } else if(resultsnap.val() === "p2 wins"){
              p2wins++
              p1losses++
          }
          database.ref("/moves").child("/move").set(1); //Bring game back to p1throw point
          $(".details").prepend("The result was: " + resultsnap.val() + "<br><br>");
          $(".details").prepend(" Player 1 chose " + throwsnap.val().p1throw.throwVal + " and player 2 chose " + throwsnap.val().p2throw.throwVal + "<br><br>");
          database.ref("/throws").remove()
          console.log(ties + " ties")
          console.log(p1wins + " p1wins")
          console.log(p2wins + " p2wins") 
          // Update results on page 
          database.ref('/results/gameresult').on("value",function(snap){
            console.log("Updating screen for both because game result has changed")
            $("#p1-wins").text(p1wins)
            $("#p2-wins").text(p2wins)
            $("#p1-losses").text(p1losses)
            $("#p2-losses").text(p2losses)
            $(".ties").text(ties)
        });
    });
});

我希望#details div中的输出能够正确更新，并且我真的不知道为什么这个错误偶尔会出现一次并且没有明确的模式吗？