javascript - slider 无法显示

Question

我的 slider 默认不显示。当我加载页面时，它是空白的。
我必须单击其中一个点才能显示幻灯片。你能帮我吗？
我认为问题出在 javascript 文件中，但找不到它。
请帮我。谢谢。

 <script>
 var slideIndex = 1;
 showSlides(slideIndex);

 function plusSlides(n) {
 showSlides(slideIndex += n);
 }

 function currentSlide(n) {
   showSlides(slideIndex = n);
 }


 function showSlides() {
    var i;
    var slides = document.getElementsByClassName("mySlides");
    for (i = 0; i < slides.length; i++) {
        slides[i].style.display = "none"; 
    }
    slideIndex++;
    if (slideIndex> slides.length) {slideIndex = 1} 
    slides[slideIndex-1].style.display = "block"; 
    setTimeout(showSlides, 2000); // Change image every 2 seconds
  }
  </script>

这是我的 HTML 代码:

    <div class="slideshow-container">
      <div class="mySlides fade">
       <div class="numbertext">1 / 3</div>

       <img src="view8.png" style="width:100%">
      <div class="title">David Lee CEO of Hing Wa Lee Group</div>

     <div class="text">David Lee has turned the Hing Wa Lee Group Into one of         the       largest luxury watch retailers in the US</div>
        <!--------BUTTON-------->
        <div id="hovers">
            <a href="#" class="buttonslider">
                <span class="contentbutslider"> Read More</span>
            </a></div>
    </div>

     <div class="mySlides fade">
       <div class="numbertext">2 / 3</div>
       <img src="view9.png" style="width:100%">
        <div class="title">One on One Business Lessons</div>
       <div class="text">Gain Access To Weekly World Entrepreneurs and their         stories to success.</div>
            <!--------BUTTON-------->
        <div id="hovers">
            <a href="#" class="buttonslider">
                <span class="contentbutslider"> Read More</span>
            </a></div>
     </div>

CSS:

     .prev, .next {
        cursor: pointer;
         position: absolute;
         top: 50%;
         width: auto;
         margin-top: -22px;
         padding: 16px;
         color: white;
         font-weight: bold;
         font-size: 28px;
         transition: 0.6s ease;
         border-radius: 0 3px 3px 0;
       }

       /* 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 title and text */
       .title {
         color: #f2f2f2;
         font-size: 58px;
         padding: 18px 22px;
         position: absolute;
         bottom: 158px;
         width: 100%;
         text-align: center;
       }
       .text {
         color: #f2f2f2;
         font-size: 28px;
         padding: 18px 22px;
         position: absolute;
         bottom: 78px;
         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: 13px;
         width: 13px;
         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 {
         -webkit-animation-name: fade;
         -webkit-animation-duration: 1.5s;
         animation-name: fade;
         animation-duration: 1.5s;
       }

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

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

此外，当我从一张幻灯片转到另一张幻灯片时，它变得越来越快，我想保持相同的速度吗？

有人可以帮忙吗？谢谢。

Answer 1

我设法创建了一个带箭头的工作自动 slider ，诀窍是

去掉setTimout，只在启动时使用setInterval函数，这样速度问题就解决了(多次触发同一个函数)。

请在下面找到一个工作片段:

var slideIndex = 1;
showSlides(slideIndex)
setInterval(function(){ showSlides(++slideIndex); }, 2000);

function plusSlides(n) {
  showSlides(slideIndex += n);
}

function currentSlide(n) {
  showSlides(slideIndex = n);
}

function showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var 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";
}

* {box-sizing:border-box}

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

.mySlides {
    display: none;
}

/* Next & previous buttons */
.prev, .next {
  cursor: pointer;
  position: absolute;
  top: 50%;
  width: auto;
  margin-top: -22px;
  padding: 16px;
  color: white;
  font-weight: bold;
  font-size: 18px;
  transition: 0.6s ease;
  border-radius: 0 3px 3px 0;
}

/* 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;
  background-color:rgba(0,0,0,0.7);
}

/* 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: 13px;
  width: 13px;
  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 {
  -webkit-animation-name: fade;
  -webkit-animation-duration: 1.5s;
  animation-name: fade;
  animation-duration: 1.5s;
}

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

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

<div class="slideshow-container">
  <div class="mySlides fade">
    <div class="numbertext">1 / 3</div>
    <img src="https://www.w3schools.com/howto/img_fjords_wide.jpg" style="width:100%">
    <div class="text">Caption Text</div>
  </div>

  <div class="mySlides fade">
    <div class="numbertext">2 / 3</div>
    <img src="https://www.w3schools.com/howto/img_nature_wide.jpg" style="width:100%">
    <div class="text">Caption Two</div>
  </div>

  <div class="mySlides fade">
    <div class="numbertext">3 / 3</div>
    <img src="https://www.w3schools.com/howto/img_mountains_wide.jpg" style="width:100%">
    <div class="text">Caption Three</div>
  </div>

  <a class="prev" onclick="plusSlides(-1)">&#10094;</a>
  <a class="next" onclick="plusSlides(1)">&#10095;</a>
</div>
<br>

<div style="text-align:center">
  <span class="dot" onclick="currentSlide(1)"></span> 
  <span class="dot" onclick="currentSlide(2)"></span> 
  <span class="dot" onclick="currentSlide(3)"></span> 
</div>