在 Javascript 中使用 getElementById.innerHTML 在 <p> 段落中显示变量值答案

【问题标题】：showing variable value in <p> paragraph using getElementById.innerHTML in Javascript在 Javascript 中使用 getElementById.innerHTML 在 <p> 段落中显示变量值
【发布时间】：2016-02-27 02:40:09
【问题描述】：

我正在尝试使用 Javascript 编写二十一点代码，并在 HTML 页面中显示结果。我已经写了逻辑，但我无法在

中显示结果

段落 ID，使用 getElementById.innerHTML。我不知道如何使它正确。你能帮我解决这个问题吗？我没时间了 :(。这是代码：

<!DOCTYPE html>
<html>
<title>Welcome to Blackjack</title>
<!--<link href="style.css" rel="stylesheet" type="text/css">

<!-- <script src="bj.js"></script> -->
<head>
<script>
var PlayerScore = 0;
var DealerScore = 0;
var Winner = "Nobody";
var AskAgain = true;

function random(maxValue)
{
 return Math.floor(Math.random() * maxValue) + 1;
}

function pickSuit()
{
 suit = random(4);

 if(suit == 1)
 return "Spades";

 if(suit == 2)
 return "Clubs";

 if(suit == 3)
 return "Diamonds";

 return "Hearts";
}

function cardName(card)
{
 if(card == 1)
 return "Ace";

 if(card == 11)
 return "Jack";

 if(card == 12)
 return "Queen";

 if(card == 13)
 return "King";

 return ("" + card);
}

function cardValue(card)
{
 if(card == 1)
 return 11;

 if(card > 10)
 return 10;

 return card;
}

function PickACard(strWho)
{
 card = random(13);
 suit = pickSuit();

 alert(strWho + " picked the " + cardName(card) + " of " + suit);

 return cardValue(card);
}

function Dealer()
{
 while(DealerScore < 17)
 {
 DealerScore = DealerScore + PickACard("Dealer");
 }
}

function User()
{
	PlayerScore = PlayerScore + PickACard("You");

}
function LookAtHands(Winner)
{
 if(DealerScore > 21)
 {
 alert("House busts! You win!");
 Winner = "You";
 }
 else
 if((PlayerScore > DealerScore) && (PlayerScore <= 21))
 {
 alert("You win!");
  Winner = "You";
 }
 else
 if(PlayerScore == DealerScore)
 {
 alert("Push!");
  Winner = "Tie";
 }
 else
 {
 alert("House wins!");
  Winner = "House";
 }
}

Dealer();
alert("Dealer's score is: " + DealerScore);
document.getElementById('DealerScore').innerHTML = DealerScore;


User();
alert("Your score is: " + PlayerScore);
document.getElementById("DealerScore").innerHTML = "Dealer's score is: " + DealerScore;


while (AskAgain == true )
{
	var answer = confirm("Do you want to draw a card?")
	if (answer == true)
	{
		User();
		alert("Your score is: " + PlayerScore);
	    document.getElementById("PlayerScore").innerHTML = "Your score is: " + PlayerScore;

		if (PlayerScore < 21)
			{AskAgain = true;}
		
		else 
			{AskAgain = false;}
	}
	else
	{
		AskAgain = false;
	}
}
LookAtHands();

 
</script>
</head>
<body>
<div><p>Welcome to our Blackjack Table!</p>
<p id="PlayerScore">Your Score is: </p>
<p id="DealerScore">Dealer's Score is: </p>
</div>

</body>
</html>

【问题讨论】：

问题不在document.getElementById("PlayerScore").innerHTML = "text"，它在你的逻辑中
据我所知，由于我将 PlayerScore 和 DealerScore 变量作为全局变量，因此运行代码 document.getElementById("PlayerScore").innerHTML = "Your score is: " + PlayerScore;应该管用！我不知道它有什么问题！ :(
@MedetTleukabiluly 怎么样？没有这些行，代码就可以正常工作。你能解释一下吗？
在浏览器控制台试试这个document.getElementById("PlayerScore").innerHTML = "text"
getElementById() 只能找到存在于 DOM 中的元素，但您的脚本位于文档正文之前，因此它在浏览器知道您的元素之前运行。尝试将脚本元素移动到关闭 </body> 标记之前，即在它尝试访问的元素之后。（你的二十一点算法也是错误的，但这是一个不同的问题。）

标签： javascript html innerhtml getelementbyid

【解决方案1】：

正如@nnnnnn 所提到的，当您的 JS 执行时甚至没有加载您的 html 标签，因此出现了问题。请尝试以下方法来解决问题：

 <!DOCTYPE html>
<html>
<title>Welcome to Blackjack</title>
<!--<link href="style.css" rel="stylesheet" type="text/css">

<!-- <script src="bj.js"></script> -->
<head>
<script>
var PlayerScore = 0;
var DealerScore = 0;
var Winner = "Nobody";
var AskAgain = true;

function random(maxValue)
{
 return Math.floor(Math.random() * maxValue) + 1;
}

function pickSuit()
{
 suit = random(4);

 if(suit == 1)
 return "Spades";

 if(suit == 2)
 return "Clubs";

 if(suit == 3)
 return "Diamonds";

 return "Hearts";
}

function cardName(card)
{
 if(card == 1)
 return "Ace";

 if(card == 11)
 return "Jack";

 if(card == 12)
 return "Queen";

 if(card == 13)
 return "King";

 return ("" + card);
}

function cardValue(card)
{
 if(card == 1)
 return 11;

 if(card > 10)
 return 10;

 return card;
}

function PickACard(strWho)
{
 card = random(13);
 suit = pickSuit();

 alert(strWho + " picked the " + cardName(card) + " of " + suit);

 return cardValue(card);
}

function Dealer()
{
 while(DealerScore < 17)
 {
 DealerScore = DealerScore + PickACard("Dealer");
 }
}

function User()
{
    PlayerScore = PlayerScore + PickACard("You");

}
function LookAtHands(Winner)
{
 if(DealerScore > 21)
 {
 alert("House busts! You win!");
 Winner = "You";
 }
 else
 if((PlayerScore > DealerScore) && (PlayerScore <= 21))
 {
 alert("You win!");
  Winner = "You";
 }
 else
 if(PlayerScore == DealerScore)
 {
 alert("Push!");
  Winner = "Tie";
 }
 else
 {
 alert("House wins!");
  Winner = "House";
 }
}
</script>
</head>
<body>
<div><p>Welcome to our Blackjack Table!</p>
<p id="PlayerScore">Your Score is: </p>
<p id="DealerScore">Dealer's Score is: </p>
</div>
<script>

Dealer();
alert("Dealer's score is: " + DealerScore);
document.getElementById('DealerScore').innerHTML = DealerScore;


User();
alert("Your score is: " + PlayerScore);
document.getElementById("DealerScore").innerHTML = "Dealer's score is: " + DealerScore;


while (AskAgain == true )
{
    var answer = confirm("Do you want to draw a card?")
    if (answer == true)
    {
        User();
        alert("Your score is: " + PlayerScore);
        document.getElementById("PlayerScore").innerHTML = "Your score is: " + PlayerScore;

        if (PlayerScore < 21)
            {AskAgain = true;}

        else 
            {AskAgain = false;}
    }
    else
    {
        AskAgain = false;
    }
}
LookAtHands();
</script>
</body>
</html>

【讨论】：

【解决方案2】：

您的脚本在包含元素的文档之前加载。将您的脚本附在：

window.onload=function() {
    //all of your JavaScript code
}

【讨论】：