我正在努力调试这张幻灯片。除了这部分我都明白了:
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';
这是 javascript 代码的最后一部分。请谁能给我逐行解释一下。我尝试过使用调试器,但不明白它是如何工作的。
这是完整的代码:
HTML:
<!-- Slideshow container -->
<div class="slideshow-container">
<!-- Full-width images with number and caption text -->
<div class="mySlides fade">
<div class="numbertext">1 / 3</div>
<img src="img1.jpg" style="width:100%">
<div class="text">Caption Text</div>
</div>
<div class="mySlides fade">
<div class="numbertext">2 / 3</div>
<img src="img2.jpg" style="width:100%">
<div class="text">Caption Two</div>
</div>
<div class="mySlides fade">
<div class="numbertext">3 / 3</div>
<img src="img3.jpg" style="width:100%">
<div class="text">Caption Three</div>
</div>
<!-- Next and previous buttons -->
<a class="prev" onclick="plusSlides(-1)">❮</a>
<a class="next" onclick="plusSlides(1)">❯</a>
</div>
<br>
<!-- The dots/circles -->
<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>
CSS:
* { box-sizing:border-box }
/* Slideshow container */
.slideshow-container {
max-width: 1000px;
position: relative;
margin: auto;
}
/* Hide the images by default */
.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;
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 {
-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}
}
JavaScript:
var slideIndex = 1;
showSlides(slideIndex);
// Next/previous controls
function plusSlides(n) {
showSlides((slideIndex += n));
}
// Thumbnail image controls
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';
}
顺便说一句,我在 w3schools.com 上找到了这个,我正在努力解决最后一部分,正如我所说的我不知道:
""
代替“活跃”?+=
标志,在这种情况下它有什么作用?请尽量让它变得简单,并提前告诉你:)
第一个
for
循环通过将 CSS 显示属性设置为“none”来隐藏所有幻灯片。第二个“for”循环使“当前”滑动按钮看起来处于非活动状态。
倒数第二行代码使上一张幻灯片 (
slides[slideIndex-1]
) 可见。最后一行使上一张幻灯片的按钮看起来处于活动状态。
我很确定我们得到了相同的作业,但答案解释了这一点,但我的代码不起作用(不显示图像),但有办法修复它吗? (无法读取未定义的属性(读取“样式”))。 不同之处在于 JavaScript 中第 2 行、第 5 行中的“var”,我使用了“let”和 double ()。