Javascript如何实现幻灯片播放功能

	
	

		
		
		

			
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@charset "UTF-8";
* {box-sizing:border-box}
body {font-family: Verdana,sans-serif;}
.mySlides {
	display:none;
  /*display 为none的含义是不展示元素，但是且不占用空间*/
}
/* 幻灯片容器 */
.slideshow-container {
 max-width: 1000px;
 position: relative;
 margin: auto;
}

/* 下一张 & 上一张 按钮 */
.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;
}

/* 定位 "下一张" 按钮靠右 */
.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);
}

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

/* 数字文本 (1/3 等) */
.numbertext {
 color: #f2f2f2;
 font-size: 12px;
 padding: 8px 12px;
 position: absolute;
 top: 0;
}

/* 标记符号 */
.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;
}

/* 淡出动画 */
.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}
}

var slideIndex = 1;

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"; 
 }//class为mySlides下的元素,即不展示项目的图片元素、数字元素和文本元素
 for (i = 0; i < dots.length; i++) {
   dots[i].className = dots[i].className.replace(" active", "");//将激活的下标元素,改为不再展示
 }
 slides[slideIndex-1].style.display = "block";//轮播的元素展示 
 dots[slideIndex-1].className += " active";//轮播图片对应下标样式激活
}
showSlides(slideIndex);