Javascript CreateElement in loop go 按下按鈕時返回上一個循環值？

Question

我正在做一個類似測驗的項目。 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。 我已經問過一個關於這個項目的問題，因為我真的不知道如何正確循環並且我解決了這個問題，但它仍然不是很好。 現在我正在創建一個以前的按鈕，它有點工作，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>

JS

    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（也可以在下一張圖片中看到）：

我試圖不創建一整套新的元素，而是回到前一組。 我嘗試使用一個簡單的 if 語句來做到這一點，例如：

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

這只是我嘗試過但沒有奏效的東西。 任何人都可以幫我這樣做嗎？

保存信息：

    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));
    })

Answer 1

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

為什么？ element.remove() - 將完全刪除 DOM 元素。 element.style.display ="none" - 只會為最終用戶隱藏它。 但它仍然會在 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

1. 下一個按鈕現在在最后一個問題上消失
2. 上一個按鈕現在在第一個問題上消失

 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('finalLink'); function NextQuestion() { 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 ADDED HERE 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' } 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"; // 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) { **//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 ADDED HERE FOR NEXT BUTTON AND PREVIOUS BUTTON CHANGES //Check if your at the last question so the prev button will stop being displayed. 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"; }

 <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>

Answer 2

您必須檢索以前創建的按鈕來顯示（*）它們。

例如，您可以使用它們的id檢索它們，該 id 放在它們的value屬性中：

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“刪除問題”時，您實際上只是在隱藏它們，而不是刪除（即從文檔中刪除）。