如何禁用在启动和Next按钮上的最后一个图像幻灯片上一页按钮

Question

如何禁用在启动和Next按钮上的最后一个图像幻灯片收藏上一页按钮......这里的链接https://www.w3schools.com/howto/tryit.asp?filename=tryhow_css_js_lightbox ..

Answer 1

添加幻灯片放映功能结束时的以下代码。

var next = document.getElementsByClassName("next")[0]; 
    var prev = document.getElementsByClassName("prev")[0]; 
    if(n == slides.length){ 
    next.classList.add('disableClass'); 
    prev.classList.remove('disableClass'); 
    } else if(n ==1){ 
    prev.classList.add('disableClass'); 
    next.classList.remove('disableClass'); 
    } else { 
    next.classList.remove('disableClass'); 
    prev.classList.remove('disableClass'); 
    } 

还添加了CSS：

.disableClass { 
    opacity: 0.2; 
    pointer-events:none; 
} 

function openModal() { 
 
    document.getElementById('myModal').style.display = "block"; 
 
} 
 

 
function closeModal() { 
 
    document.getElementById('myModal').style.display = "none"; 
 
} 
 

 
var slideIndex = 1; 
 
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("demo"); 
 
    var captionText = document.getElementById("caption"); 
 
    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"; 
 
    captionText.innerHTML = dots[slideIndex-1].alt; 
 
    
 
    var next = document.getElementsByClassName("next")[0]; 
 
    var prev = document.getElementsByClassName("prev")[0]; 
 
    if(n == slides.length){ 
 
    next.classList.add('disableClass'); 
 
    prev.classList.remove('disableClass'); 
 
    } else if(n ==1){ 
 
    prev.classList.add('disableClass'); 
 
    next.classList.remove('disableClass'); 
 
    } else { 
 
    next.classList.remove('disableClass'); 
 
    prev.classList.remove('disableClass'); 
 
    } 
 
}

body { 
 
    font-family: Verdana, sans-serif; 
 
    margin: 0; 
 
} 
 

 
* { 
 
    box-sizing: border-box; 
 
} 
 

 
.row > .column { 
 
    padding: 0 8px; 
 
} 
 

 
.row:after { 
 
    content: ""; 
 
    display: table; 
 
    clear: both; 
 
} 
 

 
.column { 
 
    float: left; 
 
    width: 25%; 
 
} 
 

 
/* The Modal (background) */ 
 
.modal { 
 
    display: none; 
 
    position: fixed; 
 
    z-index: 1; 
 
    padding-top: 100px; 
 
    left: 0; 
 
    top: 0; 
 
    width: 100%; 
 
    height: 100%; 
 
    overflow: auto; 
 
    background-color: black; 
 
} 
 

 
/* Modal Content */ 
 
.modal-content { 
 
    position: relative; 
 
    background-color: #fefefe; 
 
    margin: auto; 
 
    padding: 0; 
 
    width: 90%; 
 
    max-width: 1200px; 
 
} 
 

 
/* The Close Button */ 
 
.close { 
 
    color: white; 
 
    position: absolute; 
 
    top: 10px; 
 
    right: 25px; 
 
    font-size: 35px; 
 
    font-weight: bold; 
 
} 
 

 
.close:hover, 
 
.close:focus { 
 
    color: #999; 
 
    text-decoration: none; 
 
    cursor: pointer; 
 
} 
 

 
.mySlides { 
 
    display: none; 
 
} 
 

 
.cursor { 
 
    cursor: pointer 
 
} 
 

 
/* Next & previous buttons */ 
 
.prev, 
 
.next { 
 
    cursor: pointer; 
 
    position: absolute; 
 
    top: 50%; 
 
    width: auto; 
 
    padding: 16px; 
 
    margin-top: -50px; 
 
    color: white; 
 
    font-weight: bold; 
 
    font-size: 20px; 
 
    transition: 0.6s ease; 
 
    border-radius: 0 3px 3px 0; 
 
    user-select: none; 
 
    -webkit-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); 
 
} 
 

 
/* Number text (1/3 etc) */ 
 
.numbertext { 
 
    color: #f2f2f2; 
 
    font-size: 12px; 
 
    padding: 8px 12px; 
 
    position: absolute; 
 
    top: 0; 
 
} 
 

 
img { 
 
    margin-bottom: -4px; 
 
} 
 

 
.caption-container { 
 
    text-align: center; 
 
    background-color: black; 
 
    padding: 2px 16px; 
 
    color: white; 
 
} 
 

 
.demo { 
 
    opacity: 0.6; 
 
} 
 

 
.active, 
 
.demo:hover { 
 
    opacity: 1; 
 
} 
 

 
img.hover-shadow { 
 
    transition: 0.3s 
 
} 
 

 
.hover-shadow:hover { 
 
    box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19) 
 
} 
 

 
.disableClass { 
 
\t opacity: 0.2; 
 
    pointer-events:none; 
 
}

<h2 style="text-align:center">Lightbox</h2> 
 

 
<div class="row"> 
 
    <div class="column"> 
 
    <img src="https://www.w3schools.com/howto/img_nature.jpg" style="width:100%" onclick="openModal();currentSlide(1)" class="hover-shadow cursor"> 
 
    </div> 
 
    <div class="column"> 
 
    <img src="https://www.w3schools.com/howto/img_fjords.jpg" style="width:100%" onclick="openModal();currentSlide(2)" class="hover-shadow cursor"> 
 
    </div> 
 
    <div class="column"> 
 
    <img src="https://www.w3schools.com/howto/img_mountains.jpg" style="width:100%" onclick="openModal();currentSlide(3)" class="hover-shadow cursor"> 
 
    </div> 
 
    <div class="column"> 
 
    <img src="https://www.w3schools.com/howto/img_lights.jpg" style="width:100%" onclick="openModal();currentSlide(4)" class="hover-shadow cursor"> 
 
    </div> 
 
</div> 
 

 
<div id="myModal" class="modal"> 
 
    <span class="close cursor" onclick="closeModal()">&times;</span> 
 
    <div class="modal-content"> 
 

 
    <div class="mySlides"> 
 
     <div class="numbertext">1/4</div> 
 
     <img src="https://www.w3schools.com/howto/img_nature_wide.jpg" style="width:100%"> 
 
    </div> 
 

 
    <div class="mySlides"> 
 
     <div class="numbertext">2/4</div> 
 
     <img src="https://www.w3schools.com/howto/img_fjords_wide.jpg" style="width:100%"> 
 
    </div> 
 

 
    <div class="mySlides"> 
 
     <div class="numbertext">3/4</div> 
 
     <img src="https://www.w3schools.com/howto/img_mountains_wide.jpg" style="width:100%"> 
 
    </div> 
 
    
 
    <div class="mySlides"> 
 
     <div class="numbertext">4/4</div> 
 
     <img src="https://www.w3schools.com/howto/img_lights_wide.jpg" style="width:100%"> 
 
    </div> 
 
    
 
    <a class="prev" onclick="plusSlides(-1)">&#10094;</a> 
 
    <a class="next" onclick="plusSlides(1)">&#10095;</a> 
 

 
    <div class="caption-container"> 
 
     <p id="caption"></p> 
 
    </div> 
 

 

 
    <div class="column"> 
 
     <img class="demo cursor" src="https://www.w3schools.com/howto/img_nature_wide.jpg" style="width:100%" onclick="currentSlide(1)" alt="Nature and sunrise"> 
 
    </div> 
 
    <div class="column"> 
 
     <img class="demo cursor" src="https://www.w3schools.com/howto/img_fjords_wide.jpg" style="width:100%" onclick="currentSlide(2)" alt="Trolltunga, Norway"> 
 
    </div> 
 
    <div class="column"> 
 
     <img class="demo cursor" src="https://www.w3schools.com/howto/img_mountains_wide.jpg" style="width:100%" onclick="currentSlide(3)" alt="Mountains and fjords"> 
 
    </div> 
 
    <div class="column"> 
 
     <img class="demo cursor" src="https://www.w3schools.com/howto/img_lights_wide.jpg" style="width:100%" onclick="currentSlide(4)" alt="Northern Lights"> 
 
    </div> 
 
    </div> 
 
</div>

注：它的工作尽可能多的预期效果..