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我已經採取了一個簡單的w3學校幻燈片，編輯here由用戶Sinisake和編輯樣式刪除幻燈片計數器和標題，並編輯prev和下一個按鈕，佔用每一半幻燈片的一側，光標改變以指示點擊。上一個按鈕導致幻燈片消失
唯一的問題是，當您單擊第一張幻燈片上的「上一張」時，previousElementSibling會調用不存在的元素，整個幻燈片將消失。我知道這是因爲我改變了前一個和下一個位置，但我不知道爲什麼。
此外，我隱藏點：無，但如果我從HTML和JavaScript中刪除它們，幻燈片放映。
我知道一些關於CSS和html的知識，但在JavaScript中很新，所以我很感謝大家的耐心和幫助。
我的代碼的下方，並且頁面也在這裏舉辦：http://dominicfortunato.com/Template%20Studio%20Site/index-updated-slideshow-2.html
(function() {
init(); //on page load - show first slide, hidethe rest
function init() {
parents = document.getElementsByClassName('slideshow-container');
for (j = 0; j < parents.length; j++) {
var slides = parents[j].getElementsByClassName("mySlides");
var dots = parents[j].getElementsByClassName("dot");
slides[0].classList.add('active-slide');
dots[0].classList.add('active');
}
}
dots = document.getElementsByClassName('dot'); //dots functionality
for (i = 0; i < dots.length; i++) {
dots[i].onclick = function() {
slides = this.parentNode.parentNode.getElementsByClassName("mySlides");
for (j = 0; j < this.parentNode.children.length; j++) {
this.parentNode.children[j].classList.remove('active');
slides[j].classList.remove('active-slide');
if (this.parentNode.children[j] == this) {
index = j;
}
}
this.classList.add('active');
slides[index].classList.add('active-slide');
}
}
//prev/next functionality
links = document.querySelectorAll('.slideshow-container a');
for (i = 0; i < links.length; i++) {
links[i].onclick = function() {
current = this.parentNode;
var slides = current.getElementsByClassName("mySlides");
var dots = current.getElementsByClassName("dot");
curr_slide = current.getElementsByClassName('active-slide')[0];
curr_dot = current.getElementsByClassName('active')[0];
curr_slide.classList.remove('active-slide');
curr_dot.classList.remove('active');
if (this.className == 'next') {
if (curr_slide.nextElementSibling.classList.contains('mySlides')) {
curr_slide.nextElementSibling.classList.add('active-slide');
curr_dot.nextElementSibling.classList.add('active');
} else {
slides[0].classList.add('active-slide');
dots[0].classList.add('active');
}
}
if (this.className == 'prev') {
\t \t if (curr_slide.previousElementSibling.classList.contains('mySlides')) {
curr_slide.previousElementSibling.classList.add('active-slide');
curr_dot.previousElementSibling.classList.add('active');
} else {
slides[slides.length - 1].classList.add('active-slide');
dots[slides.length - 1].classList.add('active');
}
}
}
}
})();/* Slideshow container */
.slideshow-container {
max-width: 80%;
position: relative;
padding-top: 3%;
padding-bottom: 2%;
margin: auto;
}
/* Next & previous buttons */
.prev, .next {
cursor: url('Images/arrow.png'), w-resize;
float: left;
position: absolute;
width: 50%;
height: 90%;
margin-right: auto;
margin-left: auto;
transition: 0.3s ease;
border-radius: 0 0px 0px 0;
}
/* Position the "next button" to the right */
.next {
cursor: url('Images/arrow.png'), e-resize;
right: 0;
border-radius: 0px 0 0 0px;
}
/* On hover, add a black background color with a little bit see-through */
.prev:hover, .next:hover {
background-color: rgba(0,0,0,0);
}
.mySlides {
display:none;
}
.active-slide {
display:block;
}
.active-slide-1 {
display:block;
}
.dot {
cursor:pointer;
height: 13px;
width: 13px;
margin: 0 2px;
background-color: #bbb;
border-radius: 50%;
display: none;
transition: background-color 0.6s ease;
}
.active, .dot:hover {
background-color: #717171;
}
/* Fading animation */
.fade {
-webkit-animation-name: fade;
-webkit-animation-duration: 0.2s;
animation-name: fade;
animation-duration: 0.2s;
}
@-webkit-keyframes fade {
from {opacity: .1}
to {opacity: 1}
}
@keyframes fade {
from {opacity: .4}
to {opacity: 1}
}
.text-container {
\t z-index: 300;
\t max-width: 80%;
\t float: center;
\t text-align: left;
\t position: relative;
\t margin-right: auto;
\t margin-left: auto;
\t padding-bottom: 2%;
\t font-family:"GT Walsheim", Calibri, sans-serif;
}
.project-description {
\t width: 100%;
\t font-size: 36px;
\t margin-left: 20px;
\t font-family:"GT Walsheim", Calibri, sans-serif;
\t display: inline;
}
.project-title {
\t width: 100%;
\t display: inline;
\t margin-left: 150px;
\t text-decoration: underline;
\t font-size: 36px;
}<div class="slideshow-container">
<a class="prev" ></a>
<a class="next"></a>
<div class="mySlides fade">
<img src="http://www.w3schools.com/howto/img_mountains_wide.jpg" style="width:100%">
</div>
<div class="mySlides fade">
<img src="http://www.w3schools.com/howto/img_fjords_wide.jpg" style="width:100%">
</div>
<div class="mySlides fade">
<img src="http://www.w3schools.com/howto/img_nature_wide.jpg" style="width:100%">
</div>
<div class="mySlides fade">
<img src="http://placehold.it/1000x350" style="width:100%">
</div>
<div style="text-align:center">
<span class="dot"></span>
<span class="dot"></span>
<span class="dot"></span>
<span class="dot"></span>
</div>
</div>
<div class="text-container">
\t <div class="project-title">Rust Belt Riders</div>
\t <div class="project-description">Identity for Rust Belt Riders, a waste management and composting company from Cleveland. </div>
</div>
<br>
<div class="slideshow-container">
<a class="prev" ></a>
<a class="next"></a>
<div class="mySlides fade">
<img src="http://www.w3schools.com/howto/img_mountains_wide.jpg" style="width:100%">
</div>
<div class="mySlides fade">
<img src="http://www.w3schools.com/howto/img_fjords_wide.jpg" style="width:100%">
</div>
<div class="mySlides fade">
<img src="http://www.w3schools.com/howto/img_nature_wide.jpg" style="width:100%">
</div>
<div class="mySlides fade">
<img src="http://placehold.it/1000x350" style="width:100%">
</div>
<div style="text-align:center">
<span class="dot"></span>
<span class="dot"></span>
<span class="dot"></span>
</div>
</div>
<div class="text-container">
\t <div class="project-title">Rust Belt Riders</div>
\t <div class="project-description">Identity for Rust Belt Riders, a waste management and composting company from Cleveland. </div>
</div>
<br>
如果（curr_slide.previousElementSibling.classList.contains（ 'mySlides'）） –
非常感謝 - 我已經更新上面我的代碼，但現在前一個按鈕總是點擊到節目中的最後一張幻燈片，而不是循環播放整個幻燈片。難道我做錯了什麼？ – Dom