Question

我使用W3Schools示例来说明如何加载幻灯片，动画效果很好，但它只提供了三个点。我必须点击其中一个才能显示图片。

    var slideIndex = 0;
showSlides(slideIndex);

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;
}

/* 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="images/slideshow/canarywharf.jpg" style="width:100%">
    <div class="text">Our headquarters in London, England.</div>
  </div>

  <div class="mySlides fade">
    <div class="numbertext">2 / 3</div>
    <img src="images/slideshow/new_york.jpg" style="width:100%">
    <div class="text">The view from our offices in New York, USA.</div>
  </div>

  <div class="mySlides fade">
    <div class="numbertext">3 / 3</div>
    <img src="images/slideshow/frankfurt.jpg" style="width:100%">
    <div class="text">Our offices in Frankfurt, Germany.</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>

https://www.w3schools.com/howto/howto_js_slideshow.asp

Answer 1

我认为您的问题与加载javascript代码有关，因为您在head元素中加载它，在这种情况下，您必须确保在加载DOM时执行javascript代码。

要解决此问题，您可以在</body>标记之前加载javascript代码，以确保在执行javascript之前加载DOM

另一种方法可能是使用jQuery查看文档何时准备就绪，您可以这样做：

$( document ).ready(function() {
   showSlides(slideIndex);
});

但我更喜欢在底部加载javascript代码而不是使用jQuery来避免使用其他库。此外，在我看来它有更好的性能，因为如果javascript代码在文档的顶部执行，那么在最终用户看到实际页面之前它将是一个视觉延迟。

W3 Schools幻灯片显示不会自动加载页面

1 个答案: