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用JavaScript做动态测验教程

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使用 JavaScript 创建动态编码测验：逐步指南

本文档旨在指导开发者使用 JavaScript 创建一个动态编码测验。我们将解决一个常见问题：如何正确更新问题和选项，避免在测验过程中重复显示相同的内容。通过逐步讲解和示例代码，你将学会如何使用计数器来追踪当前问题，并动态更新测验内容。

初始化测验数据

首先，我们需要一个包含问题、选项和答案的 JavaScript 数组。每个元素都是一个对象，包含 question、choices 和 answer 属性。

var quizQuestions = [
    {
        question: "What method would you use to create a DOM object Element?", 
        choices: [".getAttribute()", ".createElement()", ".getElementById", ".setAttribute()"], 
        answer: ".createElement()"
    },
    {
        question: "What are variables used for?", 
        choices: ["Iterating over arrays", "Linking a JavaScript file to your html", "Storing data", "Performing specific tasks"], 
        answer: "Storing data"
    },
    {
        question: "When declaring a function, what comes after the keyword 'function'?", 
        choices: ["()", ";", "/", "++"], 
        answer: "()"
    }, 
    {
        question: "What would you use if you wanted to execute a block of code a set number of times?", 
        choices: ["While loop", "Math.random()", "For loop", "Switch statement"], 
        answer: "For loop"
    }, 
    {
        question: "Using the word 'break' will stop the code execution inside the switch block.", 
        choices: ["True", "False"], 
        Answer: "True"
    }
];

获取 DOM 元素

接下来，我们需要获取页面上的相关 DOM 元素，例如问题显示区域、选项按钮等。

var highScoresButtonEl = document.querySelector(".high-scores");
var startQuizEl = document.querySelector(".quiz-button");
var introTextEl = document.querySelector(".intro-text");
var questionsEl = document.querySelector(".questions");
var choicesEl = document.querySelector(".choices");
var answerEl = document.querySelector(".answer")
var timerEl = document.querySelector(".timer");

var choicesListEl = document.createElement("ul");
    choicesListEl.setAttribute("class", "choices");
    choicesEl.appendChild(choicesListEl);

初始化问题计数器

这是解决问题的关键。我们需要一个变量来跟踪当前的问题索引。

var currentQuestionIndex = 0;

显示问题和选项

现在，我们需要编写函数来显示问题和选项。关键在于使用 currentQuestionIndex 来访问 quizQuestions 数组中的正确元素。

function displayQuestion() {
    questionsEl.textContent = quizQuestions[currentQuestionIndex].question;
}

function displayChoices() {
    choicesListEl.innerHTML = ""; // 清空之前的选项

    for (let i = 0; i < quizQuestions[currentQuestionIndex].choices.length; i++) {
        var li = document.createElement("li");
        li.textContent = quizQuestions[currentQuestionIndex].choices[i];
        li.setAttribute("data-index", i); // 存储选项索引
        li.addEventListener("click", checkAnswer); // 添加点击事件监听器
        choicesListEl.appendChild(li);
    }
}

注意：

choicesListEl.innerHTML = ""; 用于在显示新问题之前清除旧的选项。
li.setAttribute("data-index", i); 将选项的索引存储在 data-index 属性中，方便后续判断答案。
li.addEventListener("click", checkAnswer); 为每个选项添加点击事件监听器，点击后调用 checkAnswer 函数。

检查答案并更新问题

checkAnswer 函数用于检查用户选择的答案是否正确，并更新问题。

function checkAnswer(event) {
    var selectedIndex = event.target.getAttribute("data-index");
    var selectedAnswer = quizQuestions[currentQuestionIndex].choices[selectedIndex];
    var correctAnswer = quizQuestions[currentQuestionIndex].answer;

    if (selectedAnswer === correctAnswer) {
        answerEl.textContent = "Correct!";
    } else {
        answerEl.textContent = "Incorrect!";
        // 在这里可以添加扣除时间的逻辑
    }

    currentQuestionIndex++; // 增加问题索引

    if (currentQuestionIndex < quizQuestions.length) {
        displayQuestion();
        displayChoices();
    } else {
        // 测验结束逻辑
        answerEl.textContent = "Quiz Complete!";
    }
}

启动测验

最后，我们需要在点击“开始测验”按钮时启动测验。

startQuizEl.addEventListener("click", function() {
    document.querySelector(".intro-text").style.visibility = "hidden";
    startQuizEl.style.visibility = "hidden";
    //startTimer(); // 启动计时器，需要自行实现
    displayQuestion();
    displayChoices();
})

完整代码示例

<!DOCTYPE html>
<html>
<head>
    <title>Coding Quiz</title>
</head>
<body>
    <header>
        <ul>
            <li><button class="high-scores" id="high-scores">High Scores</button></li>
            <li class="timer"></li>
        </ul>
    </header>
    <main>
        <div class="intro-text">
            <h1>Timed Coding Quiz</h1>
            <p>Come test your coding knowledge with this timed coding quiz! Everytime you answer a questoin incorrectly,
                8 seconds is deducted from your total time! Good luck!</p>
    </main>
    </div>
    <section class="quiz-content">
        <button class="quiz-button" id="quiz-button" type="submit">Start Quiz</button>
        <div class="questions" id="questions"></div>
        <div class="choices" id="choices"></div>
        <div class="answer" id="answer"></div>
    </section>

    <script>
        // Array of the questions, choices, and answers for the quiz.
        var quizQuestions = [
            {
                question: "What method would you use to create a DOM object Element?", 
                choices: [".getAttribute()", ".createElement()", ".getElementById", ".setAttribute()"], 
                answer: ".createElement()"
            },
            {
                question: "What are variables used for?", 
                choices: ["Iterating over arrays", "Linking a JavaScript file to your html", "Storing data", "Performing specific tasks"], 
                answer: "Storing data"
            },
            {
                question: "When declaring a function, what comes after the keyword 'function'?", 
                choices: ["()", ";", "/", "++"], 
                answer: "()"
            }, 
            {
                question: "What would you use if you wanted to execute a block of code a set number of times?", 
                choices: ["While loop", "Math.random()", "For loop", "Switch statement"], 
                answer: "For loop"
            }, 
            {
                question: "Using the word 'break' will stop the code execution inside the switch block.", 
                choices: ["True", "False"], 
                Answer: "True"
            }
        ];

        // Buttons
        var highScoresButtonEl = document.querySelector(".high-scores");
        var startQuizEl = document.querySelector(".quiz-button");

        var introTextEl = document.querySelector(".intro-text");
        var questionsEl = document.querySelector(".questions");
        var choicesEl = document.querySelector(".choices");
        var answerEl = document.querySelector(".answer")
        var timerEl = document.querySelector(".timer");

        var choicesListEl = document.createElement("ul");
            choicesListEl.setAttribute("class", "choices");
            choicesEl.appendChild(choicesListEl);

        var currentQuestionIndex = 0;

        function displayQuestion() {
            questionsEl.textContent = quizQuestions[currentQuestionIndex].question;
        }

        function displayChoices() {
            choicesListEl.innerHTML = ""; // Clear previous choices

            for (let i = 0; i < quizQuestions[currentQuestionIndex].choices.length; i++) {
                var li = document.createElement("li");
                li.textContent = quizQuestions[currentQuestionIndex].choices[i];
                li.setAttribute("data-index", i);
                li.addEventListener("click", checkAnswer);
                choicesListEl.appendChild(li);
            }
        }

        function checkAnswer(event) {
            var selectedIndex = event.target.getAttribute("data-index");
            var selectedAnswer = quizQuestions[currentQuestionIndex].choices[selectedIndex];
            var correctAnswer = quizQuestions[currentQuestionIndex].answer;

            if (selectedAnswer === correctAnswer) {
                answerEl.textContent = "Correct!";
            } else {
                answerEl.textContent = "Incorrect!";
                // Add time deduction logic here
            }

            currentQuestionIndex++;

            if (currentQuestionIndex < quizQuestions.length) {
                displayQuestion();
                displayChoices();
            } else {
                // Quiz complete logic
                answerEl.textContent = "Quiz Complete!";
            }
        }


        // Button that starts the timer, displays the first question and the first set of choices.
        startQuizEl.addEventListener("click", function() {
            document.querySelector(".intro-text").style.visibility = "hidden";
            startQuizEl.style.visibility = "hidden";
            //startTimer();
            displayQuestion();
            displayChoices();

        })
    </script>
</body>
</html>

注意事项

计时器： 上述代码中 startTimer() 函数需要你自行实现，用于实现测验的计时功能。
分数： 你可以添加一个变量来跟踪用户的分数，并在 checkAnswer 函数中根据答案是否正确来更新分数。
测验结束： 在 checkAnswer 函数中，当 currentQuestionIndex 大于等于 quizQuestions.length 时，表示测验结束。你需要添加相应的逻辑来显示最终分数、保存分数等。
错误处理： 为了提高代码的健壮性，可以添加错误处理机制，例如检查 quizQuestions 数组是否为空，或者处理用户点击选项时可能出现的异常。