HTMLButtonElement.onclick 处未捕获的 ReferenceError答案

【问题标题】：Uncaught ReferenceError at HTMLButtonElement.onclickHTMLButtonElement.onclick 处未捕获的 ReferenceError
【发布时间】：2020-09-23 08:03:49
【问题描述】：

我有一个 html 和 js 的测验代码。测验有 10 个问题，应该有按钮可以在问题之间移动。第一个问题很好，但是当我尝试回答第二个问题时，我在控制台中收到此错误： Game.html:1 Uncaught ReferenceError: num is not defined 在 HTMLButtonElement.onclick (Game.html:1)

我可以做些什么来防止这个错误？我试图将js代码复制到html中的脚本元素，但没有成功。

html的代码是这样的：

 <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Game</title>
    <script src="script.js"></script>
    <link rel="stylesheet" href="style.css">
</head>
<body id="gameBody" onload="InitGame()">

    <h1>Welcome to the game</h1>
    <h3 class="header">Your score</h3>
    <h3 class="text" id="score"></h3>
    <h5 class="header">Choose the right answer</h5>
    <p class="header">The question number</p>
    <p class="text" id="questionNumber"></p>
    <p class="header">The word you need to translate</p>
    <p id="word"></p>
    <div id="image">

    </div>
    <div id="options">

    </div>
    <p id="message"></p>
    <button class="myChoise" onclick="prevQuestion()">Previous</button>
    <button class="myChoise" onclick="nextQuestion()">Next</button>
   
</body>
</html>  ```

And in script.js I have this array of objects :

let food=[{
    'ID':1,
    'word':'What is the national dish of Italy',
    'options':[
        {name : 'פסטה, פיצה, ריזוטו'},
        {name : 'המבורגר'},
        {name : 'מרק עוף'}
    ],
    'img':'img/200.jpg',
    'rightAnswer':'פסטה, פיצה, ריזוטו',
  },
  {
    'ID':2,
    'word':'What is the national dish of the United States?',
    'options':[
        {name : 'המבורגר, נקנקיה בלחמניה, פאי '},
        {name : 'פיצה'},
        {name : 'ריזוטו'}
    ],
    'img':'img/23.jpg',
    'rightAnswer':'המבורגר, נקנקיה בלחמניה, פאי',
  },
  {
    'ID':3,
    'word':'What is the national dish of Hungary?',
    'options':[
        {name : 'גולאש'},
        {name : 'המבורגר'},
        {name : 'נקנקיה בלחמניה'}
    ],
    'img':'img/21.jpg',
    'rightAnswer':'גולאש',
  },
  {
    'ID':4,
    'word':'What is the national dish of Greece?',
    'options':[
        {name : 'מוסקה,סלט יווני'},
        {name : 'גולאש'},
        {name : 'המבורגר'}
    ],
    'img':'img/222.jpg',
    'rightAnswer':'סלט יווני,מוסקה',
  },
  {
    'ID':5,
    'word':'What is the national dish of Belarus?',
    'options':[
        {name : 'לביבה'},
        {name : 'קציצות בשר'},
        {name : 'מרק עוף'}
    ],
    'img':'img/444.jpg',
    'rightAnswer':'לביבה',
  },
  {
    'ID':6,
    'word':'What is the national dish of the United Kingdom?',
    'options':[
        {name : ' פיש אנד ציפס'},
        {name : 'ответ'},
        {name : 'название'}
    ],
    'img':'img/20.jpg',
    'rightAnswer':' פיש אנד ציפס',
  },
  {
    'ID':7,
    'word':'What is China national dish?',
    'options':[
        {name : 'אורז'},
        {name : 'קציצות בקר'},
        {name : 'המבורגר'}
    ],
    'img':'img/486.jpg',
    'rightAnswer':'אורז',
  },
  {
    'ID':8,
    'word':'What is the national dish of France?',
    'options':[
        {name : 'באגט, קרואסון, פואה גרא'},
        {name : 'נקנקיה בלחמניה'},
        {name : 'לביבות'}
    ],
    'img':'img/22.jpg',
    'rightAnswer':'באגט, קרואסון, פואה גרא',
  },
  {
    'ID':9,
    'word':'What is the national dish of Cyprus?',
    'options':[
        {name : 'חלומי'},
        {name : 'באגט'},
        {name : 'אורז'}
    ],
    'img':'img/24.jpg',
    'rightAnswer':'חלומי',
  },
  {
    'ID':10,
    'word':'What is the national dish of Mexico?',
    'options':[
        {name : 'טאקו, גואקמולי'},
        {name : 'אורז'},
        {name : 'פיש אנד ציפס'}
    ],
    'img':'img/264.jpg',
    'rightAnswer':'טאקו,גואקמולי',
  }
]


And this functions :

let score = 0;
function InitGame(){
 document.getElementById("questionNumber").innerHTML = food[0].ID;
    document.getElementById("score").innerHTML= score;
    document.getElementById("word").innerHTML= food[0].word;
    let imgSrc = food[0].img;
    let img = document.createElement("img");
    img.src = food[0].img;
    img.width = '500';
    img.height = '300';
    document.getElementById("image").appendChild(img);
    document.getElementById("options").innerHTML =
    "<button class='btn' id='1' onclick='checkAnswer(food[0].ID,this)'></button> " +
     "<button class='btn' id='2' onclick='checkAnswer(food[0].ID,this)'></button> " +
     "<button class='btn' id='3' onclick='checkAnswer(food[0].ID,this)'></button>";
    document.getElementById("options").getElementsByTagName('button')[0].innerHTML = food[0].options[0].name;
    document.getElementById("options").getElementsByTagName('button')[1].innerHTML = food[0].options[1].name;
    document.getElementById("options").getElementsByTagName('button')[2].innerHTML = food[0].options[2].name; 
}

function checkAnswer(questionNum,btn){
 for(i in food)
            {
                if(food[i].ID === questionNum)
                {
                    let chosed = btn.id;
                    let answer = food[i].options[chosed-1].name;
                    if(answer === food[i].rightAnswer)
                    {
                        score = score+1;
                        document.getElementById("score").innerHTML= score;
                        document.getElementById("message").innerHTML = "Right answer";
                        nextQuestion();
                    }
                    else
                    {
                        score = score-0.5;
                        document.getElementById("score").innerHTML= score;
                        document.getElementById("message").innerHTML = "wrong answer, please try again";
                    }
                }
            } 
}

function nextQuestion(){
   let qNum = document.getElementById("questionNumber").innerHTML;
   let num = ++qNum;
   if(num === 10)
        {
            num = 0;
        }
        document.getElementById("questionNumber").innerHTML = num;
        document.getElementById("score").innerHTML= score;
        document.getElementById("word").innerHTML= food[num].word;
        document.getElementById("image").innerHTML="";
        let imgSrc = food[num].img;
        let img = document.createElement("img");
        img.src = food[num].img;
        img.width = '500';
        img.height = '300';
        document.getElementById("image").appendChild(img);
        document.getElementById("options").innerHTML="";
        document.getElementById("options").innerHTML =
        "<button class='btn' id='1' onclick='checkAnswer(food[num].ID,this)'></button> " +
        "<button class='btn' id='2' onclick='checkAnswer(food[num].ID,this)'></button> " +
        "<button class='btn' id='3' onclick='checkAnswer(food[num].ID,this)'></button>";
        document.getElementById("options").getElementsByTagName('button')[0].innerHTML = food[num].options[0].name;
        document.getElementById("options").getElementsByTagName('button')[1].innerHTML = food[num].options[1].name;
        document.getElementById("options").getElementsByTagName('button')[2].innerHTML = food[num].options[2].name;

}


function prevQuestion(){
 let qNum = document.getElementById("questionNumber").innerHTML;
        let num = --qNum;
if(num === -1)
        {
            num = 10;
        }
        document.getElementById("questionNumber").innerHTML = num;
        document.getElementById("score").innerHTML= score;
        document.getElementById("word").innerHTML= food[num].word;
        document.getElementById("image").innerHTML="";
        let imgSrc = food[num].img;
        let img = document.createElement("img");
        img.src = food[num].img;
        img.width = '500';
        img.height = '300';
        document.getElementById("image").appendChild(img);
        document.getElementById("options").innerHTML="";
        document.getElementById("options").innerHTML =
        `<button class='btn' id='1' onclick='checkAnswer(food[num].ID,this)'></button> <button class='btn' id='2' onclick='checkAnswer(food[num].ID,this)'></button> <button class='btn' id='3' onclick='checkAnswer(food[num].ID,this)'></button>`;
        document.getElementById("options").getElementsByTagName('button')[0].innerHTML = food[num].options[0].name;
        document.getElementById("options").getElementsByTagName('button')[1].innerHTML = food[num].options[1].name;
        document.getElementById("options").getElementsByTagName('button')[2].innerHTML = food[num].options[2].name;
}

【问题讨论】：

标签： javascript html error-handling

【解决方案1】：

你得到num is not defined的原因是你设置了像'checkAnswer(food[num].ID,this)'这样的内部HTML，在这种情况下，数字没有引用函数中的num变量，你应该使用'checkAnswer(food[" + num + "].ID,this)'，这样当html呈现时而不是 num 它将呈现像这样的数字 checkAnswer(food[9].ID,this)

let food = [{
    'ID': 1,
    'word': 'What is the national dish of Italy',
    'options': [{
        name: 'פסטה, פיצה, ריזוטו'
      },
      {
        name: 'המבורגר'
      },
      {
        name: 'מרק עוף'
      }
    ],
    'img': 'img/200.jpg',
    'rightAnswer': 'פסטה, פיצה, ריזוטו',
  },
  {
    'ID': 2,
    'word': 'What is the national dish of the United States?',
    'options': [{
        name: 'המבורגר, נקנקיה בלחמניה, פאי'
      },
      {
        name: 'פיצה'
      },
      {
        name: 'ריזוטו'
      }
    ],
    'img': 'img/23.jpg',
    'rightAnswer': 'המבורגר, נקנקיה בלחמניה, פאי',
  },
  {
    'ID': 3,
    'word': 'What is the national dish of Hungary?',
    'options': [{
        name: 'גולאש'
      },
      {
        name: 'המבורגר'
      },
      {
        name: 'נקנקיה בלחמניה'
      }
    ],
    'img': 'img/21.jpg',
    'rightAnswer': 'גולאש',
  },
  {
    'ID': 4,
    'word': 'What is the national dish of Greece?',
    'options': [{
        name: 'מוסקה,סלט יווני'
      },
      {
        name: 'גולאש'
      },
      {
        name: 'המבורגר'
      }
    ],
    'img': 'img/222.jpg',
    'rightAnswer': 'מוסקה,סלט יווני',
  },
  {
    'ID': 5,
    'word': 'What is the national dish of Belarus?',
    'options': [{
        name: 'לביבה'
      },
      {
        name: 'קציצות בשר'
      },
      {
        name: 'מרק עוף'
      }
    ],
    'img': 'img/444.jpg',
    'rightAnswer': 'לביבה',
  },
  {
    'ID': 6,
    'word': 'What is the national dish of the United Kingdom?',
    'options': [{
        name: ' פיש אנד ציפס'
      },
      {
        name: 'ответ'
      },
      {
        name: 'название'
      }
    ],
    'img': 'img/20.jpg',
    'rightAnswer': ' פיש אנד ציפס',
  },
  {
    'ID': 7,
    'word': 'What is China national dish?',
    'options': [{
        name: 'אורז'
      },
      {
        name: 'קציצות בקר'
      },
      {
        name: 'המבורגר'
      }
    ],
    'img': 'img/486.jpg',
    'rightAnswer': 'אורז',
  },
  {
    'ID': 8,
    'word': 'What is the national dish of France?',
    'options': [{
        name: 'באגט, קרואסון, פואה גרא'
      },
      {
        name: 'נקנקיה בלחמניה'
      },
      {
        name: 'לביבות'
      }
    ],
    'img': 'img/22.jpg',
    'rightAnswer': 'באגט, קרואסון, פואה גרא',
  },
  {
    'ID': 9,
    'word': 'What is the national dish of Cyprus?',
    'options': [{
        name: 'חלומי'
      },
      {
        name: 'באגט'
      },
      {
        name: 'אורז'
      }
    ],
    'img': 'img/24.jpg',
    'rightAnswer': 'חלומי',
  },
  {
    'ID': 10,
    'word': 'What is the national dish of Mexico?',
    'options': [{
        name: 'טאקו,גואקמולי'
      },
      {
        name: 'אורז'
      },
      {
        name: 'פיש אנד ציפס'
      }
    ],
    'img': 'img/264.jpg',
    'rightAnswer': 'טאקו,גואקמולי',
  }
]

let score = 0;

function InitGame() {
  document.getElementById("questionNumber").innerHTML = food[0].ID;
  document.getElementById("score").innerHTML = score;
  document.getElementById("word").innerHTML = food[0].word;
  let imgSrc = food[0].img;
  let img = document.createElement("img");
  img.src = food[0].img;
  img.width = '500';
  img.height = '300';
  document.getElementById("image").appendChild(img);
  document.getElementById("options").innerHTML =
    "<button class='btn' id='1' onclick='checkAnswer(food[0].ID,this)'></button> " +
    "<button class='btn' id='2' onclick='checkAnswer(food[0].ID,this)'></button> " +
    "<button class='btn' id='3' onclick='checkAnswer(food[0].ID,this)'></button>";
  document.getElementById("options").getElementsByTagName('button')[0].innerHTML = food[0].options[0].name;
  document.getElementById("options").getElementsByTagName('button')[1].innerHTML = food[0].options[1].name;
  document.getElementById("options").getElementsByTagName('button')[2].innerHTML = food[0].options[2].name;
}

function checkAnswer(questionNum, btn) {
  debugger
  for (i in food) {
    if (food[i].ID === questionNum) {
      let chosed = btn.id;
      let answer = food[i].options[chosed - 1].name;
      if (answer === food[i].rightAnswer) {
        score = score + 1;
        document.getElementById("score").innerHTML = score;
        document.getElementById("message").innerHTML = "Right answer";
        nextQuestion();
      } else {
        score = score - 0.5;
        document.getElementById("score").innerHTML = score;
        document.getElementById("message").innerHTML = "wrong answer, please try again";
      }
    }
  }
}

function nextQuestion() {
  let qNum = document.getElementById("questionNumber").innerHTML;
  let num = ++qNum;
  if (num === 10) {
    num = 0;
  }
  document.getElementById("questionNumber").innerHTML = num;
  document.getElementById("score").innerHTML = score;
  document.getElementById("word").innerHTML = food[num].word;
  document.getElementById("image").innerHTML = "";
  let imgSrc = food[num].img;
  let img = document.createElement("img");
  img.src = food[num].img;
  img.width = '500';
  img.height = '300';
  document.getElementById("image").appendChild(img);
  document.getElementById("options").innerHTML = "";
  document.getElementById("options").innerHTML =
    "<button class='btn' id='1' onclick='checkAnswer(food[" + num + "].ID,this)'></button> " +
    "<button class='btn' id='2' onclick='checkAnswer(food[" + num + "].ID,this)'></button> " +
    "<button class='btn' id='3' onclick='checkAnswer(food[" + num + "].ID,this)'></button>";
  document.getElementById("options").getElementsByTagName('button')[0].innerHTML = food[num].options[0].name;
  document.getElementById("options").getElementsByTagName('button')[1].innerHTML = food[num].options[1].name;
  document.getElementById("options").getElementsByTagName('button')[2].innerHTML = food[num].options[2].name;
  debugger;
}


function prevQuestion() {
  let qNum = document.getElementById("questionNumber").innerHTML;
  let num = --qNum;
  if (num === -1) {
    num = 10;
  }
  document.getElementById("questionNumber").innerHTML = num;
  document.getElementById("score").innerHTML = score;
  document.getElementById("word").innerHTML = food[num].word;
  document.getElementById("image").innerHTML = "";
  let imgSrc = food[num].img;
  let img = document.createElement("img");
  img.src = food[num].img;
  img.width = '500';
  img.height = '300';
  document.getElementById("image").appendChild(img);
  document.getElementById("options").innerHTML = "";
  document.getElementById("options").innerHTML =
    `<button class='btn' id='1' onclick='checkAnswer(food[` + num + `].ID,this)'></button> <button class='btn' id='2' onclick='checkAnswer(food[` + num + `].ID,this)'></button> <button class='btn' id='3' onclick='checkAnswer(food[` + num + `].ID,this)'></button>`;
  document.getElementById("options").getElementsByTagName('button')[0].innerHTML = food[num].options[0].name;
  document.getElementById("options").getElementsByTagName('button')[1].innerHTML = food[num].options[1].name;
  document.getElementById("options").getElementsByTagName('button')[2].innerHTML = food[num].options[2].name;
}

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Game</title>
</head>

<body id="gameBody" onload="InitGame()">

  <h1>Welcome to the game</h1>
  <h3 class="header">Your score</h3>
  <h3 class="text" id="score"></h3>
  <h5 class="header">Choose the right answer</h5>
  <p class="header">The question number</p>
  <p class="text" id="questionNumber"></p>
  <p class="header">The word you need to translate</p>
  <p id="word"></p>
  <div id="image">

  </div>
  <div id="options">

  </div>
  <p id="message"></p>
  <button class="myChoise" onclick="prevQuestion()">Previous</button>
  <button class="myChoise" onclick="nextQuestion()">Next</button>

</body>

</html>

【讨论】：