无法用点分页控制幻灯片放映图像

问题描述 投票：0回答：1

我需要正确控制滑块图像与底部点分页。但我在代码中遗漏了一些东西或做错了。

您可以在此处查看工作演示 - https://playcode.io/2070692

整个代码是-

HTML：

    <!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta
            name="viewport"
            content="width=device-width, initial-scale=1.0"
        />
        <title>Slideshow with JS</title>
        <link
            rel="stylesheet"
            href="app.css"
        />
    </head>
    <body>
        <div class="slideshow-container">
            <div class="mySlides fade">
                <div class="numbertext">1 / 4</div>
                <img
                    src="img/img_nature_wide.jpg"
                    style="width: 100%"
                />
                <div class="text">Caption Text</div>
            </div>

            <div class="mySlides fade">
                <div class="numbertext">2 / 4</div>
                <img
                    src="img/img_snow_wide.jpg"
                    style="width: 100%"
                />
                <div class="text">Caption Two</div>
            </div>

            <div class="mySlides fade">
                <div class="numbertext">3 / 4</div>
                <img
                    src="img/img_mountains_wide.jpg"
                    style="width: 100%"
                />
                <div class="text">Caption Three</div>
            </div>

            <div class="mySlides fade">
                <div class="numbertext">4/4</div>
                <img
                    src="img/img_lights_wide.jpg"
                    style="width: 100%"
                />
                <div class="text">Caption Four</div>
            </div>

            <a class="prev">❮</a>
            <a class="next">❯</a>
        </div>
        <br />

        <div style="text-align: center">
            <span class="dot"></span>
            <span class="dot"></span>
            <span class="dot"></span>
            <span class="dot"></span>
        </div>

        <script src="app.js"></script>
    </body>
</html>

CSS：

    * {box-sizing: border-box}
body {font-family: Verdana, sans-serif; margin:0}
.mySlides {display: none}
img {vertical-align: middle;}

/* Slideshow container */
.slideshow-container {
  max-width: 1000px;
  position: relative;
  margin: auto;
}

/* Next & previous buttons */
.prev, .next {
  cursor: pointer;
  position: absolute;
  top: 50%;
  width: auto;
  padding: 16px;
  margin-top: -22px;
  color: white;
  font-weight: bold;
  font-size: 18px;
  transition: 0.6s ease;
  border-radius: 0 3px 3px 0;
  user-select: none;
}

/* Position the "next button" to the right */
.next {
  right: 0;
  border-radius: 3px 0 0 3px;
}

/* On hover, add a black background color with a little bit see-through */
.prev:hover, .next:hover {
  background-color: rgba(0,0,0,0.8);
}

/* Caption text */
.text {
  color: #f2f2f2;
  font-size: 15px;
  padding: 8px 12px;
  position: absolute;
  bottom: 8px;
  width: 100%;
  text-align: center;
}

/* Number text (1/3 etc) */
.numbertext {
  color: #f2f2f2;
  font-size: 12px;
  padding: 8px 12px;
  position: absolute;
  top: 0;
}

/* The dots/bullets/indicators */
.dot {
  cursor: pointer;
  height: 15px;
  width: 15px;
  margin: 0 2px;
  background-color: #bbb;
  border-radius: 50%;
  display: inline-block;
  transition: background-color 0.6s ease;
}

.active, .dot:hover {
  background-color: #717171;
}

/* Fading animation */
.fade {
  animation-name: fade;
  animation-duration: 1.5s;
}

@keyframes fade {
  from {opacity: .4} 
  to {opacity: 1}
}

/* On smaller screens, decrease text size */
@media only screen and (max-width: 300px) {
  .prev, .next,.text {font-size: 11px}
}

JS：

const showSlides = (n) => {
    let i;
    let slides = document.getElementsByClassName('mySlides');
    let dots = document.getElementsByClassName('dot');
    if (n > slides.length) {
        slideIndex = 1;
    }
    if (n < 1) {
        slideIndex = slides.length;
    }
    for (i = 0; i < slides.length; i++) {
        slides[i].style.display = 'none';
    }
    for (i = 0; i < dots.length; i++) {
        dots[i].className = dots[i].className.replace(' active', '');
    }
    slides[slideIndex - 1].style.display = 'block';
    dots[slideIndex - 1].className += ' active';
};

showSlides(slideIndex);

document.querySelector('.prev').addEventListener('click', () => {
    console.log('clicked');
    showSlides((slideIndex += -1));
});

document.querySelector('.next').addEventListener('click', () => {
    console.log('clicked');
    showSlides((slideIndex += 1));
});

const currentSlide = (n) => {
    showSlides((slideIndex = n));
};

const dots = document.querySelectorAll('.dot');

dots.forEach((dot) => {
    dot.addEventListener('click', () => {
        console.log(`${slideIndex}`);
        currentSlide(slideIndex + 1);
    });
});

现在我想使用点分页控制幻灯片，您也可以查看演示，但它没有按预期工作。我怀疑JS代码的问题出在这部分。

const dots = document.querySelectorAll('.dot');

dots.forEach((dot) => {
    dot.addEventListener('click', () => {
        console.log(`${slideIndex}`);
        currentSlide(slideIndex + 1);
    });
});
javascript arrays
1个回答
0
投票

假设您的问题是，当您单击这些点时，图像会像单击错误时一样继续：

问题是，在处理点上的点击时，您将下一张幻灯片设置为 currentSlide + 1，因此正是执行下一个按钮的操作

相反，您必须将其设置为点的索引：

dots.forEach((dot, index) => {
  dot.addEventListener('click', () => {
    console.log(`${index}`);
    currentSlide(index + 1);
  });
});

请注意，将索引设置为各个点 html 元素的属性，然后将它们用作索引可能会更清晰

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