按下按鈕時，回圈中的JavascriptCreateElement會回傳上一個回圈值嗎？-有解無憂

我正在做一個類似測驗的專案。您會收到多個問題和答案，您可以單擊任何答案來創建個人結果。我已經問過一個關于這個專案的問題，因為我真的不知道如何正確回圈，我解決了這個問題，但它仍然不是很好。現在我正在創建一個前一個按鈕，它有點作業，但不是很好。

我的代碼：

<div class="container">
    <div id="question"></div>
    <div id="answer"></div>
    <button onclick="NextQuestion()" id="nextbtn">Next</button>
    <button onclick="PrevQuestion()" id="prevbtn">Previous</button>
    <div id="finalLink"></div>
</div>

    class QuizPart{
        constructor(questionDescription, chosenAnswer, prefix){
            this.questionDescription = questionDescription;
            this.chosenAnswer = chosenAnswer;
            this.prefix = prefix;
        }
    }
    
    class ChosenAnswer{
        constructor(id, name){
            this.id = id;
            this.name = name;
        }
    }

    let Quiz = [
        new QuizPart('Whats your size?', [
            new ChosenAnswer('6595', '41'),
            new ChosenAnswer('6598', '42'),
            new ChosenAnswer('6601', '43'),
        ], 'bd_shoe_size_ids='),

        new QuizPart('What color would you like?', [
            new ChosenAnswer('6053', 'Red'),
            new ChosenAnswer('6044', 'Blue'),
            new ChosenAnswer('6056', 'Yellow'),
            new ChosenAnswer('6048', 'Green'),
        ], 'color_ids='),

        new QuizPart('What brand would you like?', [
            new ChosenAnswer('5805', 'Adidas'),
            new ChosenAnswer('5866', 'Nike'),
            new ChosenAnswer('5875', 'Puma'),
        ], 'manufacturer_ids='),
    ]
    // console.log(Quiz);

    let url = [];

    let questionNumber = 0;
    let button = document.getElementById('answer');
    let questionName = document.getElementById('question');
    let nextbtn = document.getElementById('nextbtn');
    let prevbtn = document.getElementById('prevbtn')
    let resultbtn = document.getElementById('FLink');

    function NextQuestion() {
        let oldAnswerButton = document.querySelectorAll('.filter_anwser');

        // Deletes old question when the next question is clicked
        for (let answerButton of oldAnswerButton) {
            answerButton.style.display = 'none';
        }

        let question = Quiz[questionNumber];

        // Displays answers of the questions
        for (let y = 0; y < question.chosenAnswer.length; y  ) {
            let item = question.chosenAnswer[y];
            // Display answer buttons
            let btn = document.createElement('button');
            btn.value = item.id;
            btn.className = "filter_anwser";
            btn.textContent = item.name;
            button.appendChild(btn);
        }
        // Check if your at the last question so the next button will stop being displayed.
        if (Quiz.length - 1 === questionNumber) {
            nextbtn.style.display = 'none';
            resultbtn.style.display = 'grid';
        }

        // Displays Question
        questionName.textContent = question.questionDescription;
        questionName.id = "questionID";

        // adds 1 to question to see a different question
        questionNumber  ;
    }

    function PrevQuestion(){
        questionNumber--;
        let oldAnswerButton = document.querySelectorAll('.filter_anwser');

        // Deletes old question when the next question is clicked
        for (let answerButton of oldAnswerButton) {
            answerButton.style.display = 'none';
        }

        let question = Quiz[questionNumber];

        // Displays answers of the questions
        for (let y = 0; y < question.chosenAnswer.length; y  ) {
            let item = question.chosenAnswer[y];
            // Display answer buttons
            let btn = document.createElement('button');
            btn.value = item.id;
            btn.className = "filter_anwser";
            btn.textContent = item.name;
            button.appendChild(btn);
        }
        //Check if your at the last question so the next button will stop being displayed.
        if (Quiz.length === questionNumber) {
            prevbtn.style.display = 'none';
            resultbtn.style.display = 'grid';
        }

        // Displays Question
        questionName.textContent = question.questionDescription;
        questionName.id = "questionID";
    }

現在你可以看到，當我按下上一個按鈕時，我創建了一個新元素（也見下圖）：按下按鈕時，回圈中的 Javascript CreateElement 會回傳上一個回圈值嗎？

我試圖不創建一組全新的元素，而是回到上一組。我試著用一個簡單的 if 陳述句來做，比如：

let i = 0;
if (i < question.chosenAnswer[y]){
    y--;
}

這只是我嘗試過但沒有奏效的事情。有人可以幫我做這個嗎？

保存資訊：

    function getLink(url) {
        let tmp = [];
        for (let i = 0; i < url.length; i  ) {
            // Check if question is from the same quiz part and adds a , between chosen answers and add the right prefix at the beginning
            if (url[i].length > 0){
                tmp.push(""   Quiz[i].prefix   url[i].join(","))
            }
        }
        /// If answers are from different quiz parts add a & between answers.
        console.log(url, questionNumber);
        return ""   tmp.join("&");
    };

    button.addEventListener("click", function (e) {
        const tgt = e.target;

        // clear the url array if there's nothing clicked
        if (url.length < questionNumber) {
            url.push([]);
        }

        let quizUrl = url[questionNumber - 1];

        // Check if a button is clicked. Changes color and adds value to the url array.
        if (quizUrl.indexOf(tgt.value) === -1) {
            quizUrl.push(tgt.value);
            e.target.style.backgroundColor = "orange";
        // Check if a button is clicked again. If clicked again changes color back and deletes value in the url array.
        } else {
            quizUrl.splice(quizUrl.indexOf(tgt.value), 1);
            e.target.style.backgroundColor = "white";
        }
        console.log(getLink(url));
    })

uj5u.com熱心網友回復：

您必須檢索先前創建的按鈕以顯示 (*) 它們。

例如，您可以使用它們id的value屬性來檢索它們：

for (let y = 0; y < question.chosenAnswer.length; y  ) {
    let item = question.chosenAnswer[y];
    // retrieve the button by it's value="id" attribute
    let btn = document.querySelector('button[value="'   item.id   '"]');
    btn.style.display = 'grid';
}

(*) 請注意，當您說“洗掉問題”時，您實際上只是在隱藏它們，而不是洗掉（即從檔案中洗掉）。

uj5u.com熱心網友回復：

您需要使用 element.remove() 而不是 element.style.display ="none"

為什么？element.remove() - 將完全洗掉 DOM 元素。element.style.display ="none" - 只會為最終用戶隱藏它。但它仍然會出現在 DOM 樹上。

Js Fiddle 的解決方案如下：

還修復了您代碼中的一些問題。在我修復的地方添加了注釋行

下一步按鈕現在在最后一個問題上消失
上一個按鈕現在在第一個問題上消失

編輯：

用很少的邏輯更改編輯了代碼片段。現在答案按預期保留在陣列中。雖然按鈕不保留顏色。這可以在上一個和下一個按鈕單擊函式中以與執行 getLinks 方法相同的方式處理。

class QuizPart{
        constructor(questionDescription, chosenAnswer, prefix){
            this.questionDescription = questionDescription;
            this.chosenAnswer = chosenAnswer;
            this.prefix = prefix;
        }
    }
    
    class ChosenAnswer{
        constructor(id, name){
            this.id = id;
            this.name = name;
        }
    }

    let Quiz = [
        new QuizPart('Whats your size?', [
            new ChosenAnswer('6595', '41'),
            new ChosenAnswer('6598', '42'),
            new ChosenAnswer('6601', '43'),
        ], 'bd_shoe_size_ids='),

        new QuizPart('What color would you like?', [
            new ChosenAnswer('6053', 'Red'),
            new ChosenAnswer('6044', 'Blue'),
            new ChosenAnswer('6056', 'Yellow'),
            new ChosenAnswer('6048', 'Green'),
        ], 'color_ids='),

        new QuizPart('What brand would you like?', [
            new ChosenAnswer('5805', 'Adidas'),
            new ChosenAnswer('5866', 'Nike'),
            new ChosenAnswer('5875', 'Puma'),
        ], 'manufacturer_ids='),
    ]
    //console.log(Quiz);

    let url = [];
    
            //FIX - INIT VALUE UPDATED TO -1
    let questionNumber = -1;
    let button = document.getElementById('answer');
    let questionName = document.getElementById('question');
    let nextbtn = document.getElementById('nextbtn');
    let prevbtn = document.getElementById('prevbtn')
    let resultbtn = document.getElementById('finalLink');

    function NextQuestion() {
            //FIX - PUSHED THIS LINE UP HERE TO HAVE SYNCED LOGIC 
            // adds 1 to question to see a different question
        questionNumber  ;


        let oldAnswerButton = document.querySelectorAll('.filter_anwser');

        // Deletes old question when the next question is clicked
        for (let answerButton of oldAnswerButton) {
           //CORRECTION DONE HERE
           answerButton.remove();
        }

        let question = Quiz[questionNumber];

        // Displays answers of the questions
        for (let y = 0; y < question.chosenAnswer.length; y  ) {
            let item = question.chosenAnswer[y];
            // Display answer buttons
            let btn = document.createElement('button');
            btn.value = item.id;
            btn.className = "filter_anwser";
            btn.textContent = item.name;
            button.appendChild(btn);
        }
        //FIX -FOR NEXT BUTTON AND PREVIOUS BUTTON CHANGES
        // Check if your at the last question so the next button will stop being displayed.

        if (questionNumber > 0 ) {
                prevbtn.style.display = 'grid'
        }else{
            prevbtn.style.display = 'none'
        }
        if (Quiz.length - 1 <= questionNumber) {
            nextbtn.style.display = 'none';
            resultbtn.style.display = 'grid';
        }else{
                nextbtn.style.display = 'grid';
        }

        // Displays Question
        questionName.textContent = question.questionDescription;
        questionName.id = "questionID";

        
    }

    function PrevQuestion(){

        questionNumber--;
        let oldAnswerButton = document.querySelectorAll('.filter_anwser');

        // Deletes old question when the next question is clicked
        for (let answerButton of oldAnswerButton) {
           //CORRECTION DONE HERE
            answerButton.remove();
        }

        let question = Quiz[questionNumber];

        // Displays answers of the questions
        for (let y = 0; y < question.chosenAnswer.length; y  ) {
            let item = question.chosenAnswer[y];
            // Display answer buttons
            let btn = document.createElement('button');
            btn.value = item.id;
            btn.className = "filter_anwser";
            btn.textContent = item.name;
            button.appendChild(btn);
        }
        //FIX - FOR NEXT BUTTON AND PREVIOUS BUTTON CHANGES
        //Check if your at the last question so the prev button will stop being displayed.
        console.log(questionNumber);
        if (questionNumber < Quiz.length - 1) {
                nextbtn.style.display = 'grid';
        }
        if (questionNumber <= 0) {
            prevbtn.style.display = 'none';
        }else{
                prevbtn.style.display = 'grid';
        }

        // Displays Question
        questionName.textContent = question.questionDescription;
        questionName.id = "questionID";
    }
    
    function getLink(url) {
    let tmp = [];
    for (let i = 0; i < url.length; i  ) {
        // Check if question is from the same quiz part and adds a , between chosen answers and add the right prefix at the beginning
        if (url[i].length > 0){
            tmp.push(""   Quiz[i].prefix   url[i].join(","))
        }
    }
    /// If answers are from different quiz parts add a & between answers.
    console.log(url, questionNumber);
    return ""   tmp.join("&");
};

button.addEventListener("click", function (e) {
    const tgt = e.target;
            
    //FIX - CLICK HANDLING ONLY FOR YOUR answer BUTTONS
    if("filter_anwser" == e.target.className){
    //FIX -  since Counter logic was update above, hence updated condition check here too
        // clear the url array if there's nothing clicked
      if (url.length < questionNumber   1) {
          url.push([]);
      }

      let quizUrl = url[questionNumber];

      // Check if a button is clicked. Changes color and adds value to the url array.
      if (quizUrl.indexOf(tgt.value) === -1) {
          quizUrl.push(tgt.value);
          e.target.style.backgroundColor = "orange";
      // Check if a button is clicked again. If clicked again changes color back and deletes value in the url array.
      } else {
          quizUrl.splice(quizUrl.indexOf(tgt.value), 1);
          e.target.style.backgroundColor = "white";
      }
      console.log(getLink(url));        
    }

})

<div class="container">
    <div id="question"></div>
    <div id="answer"></div>
    <button onclick="NextQuestion()" id="nextbtn">Next</button>
    <!--At first there should not be a previous button Hence update this-->        
    <button onclick="PrevQuestion()" id="prevbtn">Previous</button>
    <div id="finalLink"></div>
</div>

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標籤：javascript 循环 if 语句创建元素

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