Javascript 干扰 CSS 转换

Question

I've recently started work on a basic landing-page website. Part of the page is a basic image slider with both the auto-nav and the manual nav being powered by JS. I got everything working but for one thing: I just can't figure out how to get the smooth transition between images - as seen in this example - to work. I figured out the problem after reading some related questions on Stackoverflow: To make the Slideshow work I'm using slides[i].style.display = "none"; and slides[slideIndex-1].style.display = "block"; to update the css code handling the 'display' element - this over rights the 'transition: 2s' css code one would need for the simple slide animation as seen in the video. As I'm terribly new to Web development I could not wrap my head around possible solutions posted here on Stackoverflow and would really appreciate anyone that could help me out with an answer to my specific problem or an alternative way to solve it.

Cheers, Jerome

 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("item"); 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"; } //automatic var slideIndexAuto = 0; showSlidesAuto(); function showSlidesAuto() { var i; var slides = document.getElementsByClassName("item"); var dots = document.getElementsByClassName("dot"); for (i = 0; i < slides.length; i++) { slides[i].style.display = "none"; dots[i].className = dots[i].className.replace(" active", ""); } slideIndexAuto++; if (slideIndexAuto > slides.length) { slideIndexAuto = 1 } slides[slideIndexAuto - 1].style.display = "block"; dots[slideIndexAuto - 1].className += " active"; setTimeout(showSlidesAuto, 5000); }

 .slider { width: 65%; max-width: 940px; height: 500px; border-radius: 0.25rem; position: relative; overflow: hidden; } .slider .left-slide, .slider .right-slide { position: absolute; height: 40px; width: 40px; background-color: #444444; border-radius: 50%; color: #ffffff; font-size: 20px; top: 50%; cursor: pointer; margin-top: -20px; text-align: center; line-height: 40px; } .slider .left-slide:hover, .slider .right-slide:hover { box-shadow: 0px 0px 10px black; background-color: #29a8e2; } .slider .left-slide { left: 30px; } .slider .right-slide { right: 30px; } .slider .slider-items .item img { width: 100%; height: 500px; display: block; } .slider .slider-items .item { position: relative; transition: 4s; } .slider .slider-items .item .caption { position: absolute; width: 100%; height: 100%; bottom: 0px; left: 0px; background-color: rgba(0, 0, 0, .5); }

 <div class="slider"> <div class="slider-items"> <div class="item fade"> <img src="/images/cs-slider-high.jpg" /> <div class="caption"> <p class="caption-text">COMING</p> <p class="caption-text">OKTOBER 10th</p> </div> </div> <div class="item fade"> <img src="/images/building-slider.jpg" /> <div class="caption"> <p class="caption-text-2">Blackstoneroad 109</br> </p> </div> </div> <div class="item fade"> <img src="/images/kontact-slider.jpg" /> <div class="caption"> <p class="caption-text-3">Coffee<br>Drinks<br>Food<br>& More</p> </div> </div> <div class="item fade"> <img src="/images/seminar-slider.jpg" /> <div class="caption"> <p class="caption-text-3">Seminar Rooms<br>Inspiration<br>Shopping<br>& More</p> </div> </div> </div> <!-- Next and previous buttons --> <a class="prev" onclick="plusSlides(-1)">&#10094;</a> <a class="next" onclick="plusSlides(1)">&#10095;</a> </div> <!-- The dots/circles --> <div class="align-text-center"> <span class="dot" onclick="currentSlide(1)"></span> <span class="dot" onclick="currentSlide(2)"></span> <span class="dot" onclick="currentSlide(3)"></span> <span class="dot" onclick="currentSlide(3)"></span> </div>

Answer 1

How is this: http://jsfiddle.net/lharby/qox05y96/

For simplification I have stripped out the dot animation (although that code is closer to the effect you want).

Here is the simplified JS:

function showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("item");
  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].classList.remove('active'); // this is updated
  }
  slides[slideIndex - 1].className += " active";
}

//automatic
var slideIndexAuto = 0;
showSlidesAuto();

function showSlidesAuto() {
  var i;
  var slides = document.getElementsByClassName("item");
  var dots = document.getElementsByClassName("dot");
  for (i = 0; i < slides.length; i++) {
    slides[i].classList.remove('active'); // this is updated
    
  }
  slideIndexAuto++;
  if (slideIndexAuto > slides.length) {
    slideIndexAuto = 1
  }
  slides[slideIndexAuto - 1].classList.add('active'); // this is updated
  setTimeout(showSlidesAuto, 4000);
}

This means we also have to change the css. display none/block is harder to animate with css transitions . So I have used opacity: 0/1 and visibility: hidden/visible . However one other trade off is that that the item elements cannot be positioned relatively this would stack them on top of one another (or side by side) usually for an animated slideshow you would use position absolute for each slide, but I realise that causes you another issue.

CSS:

.slider .slider-items .item {
    visibility: hidden;
    opacity: 0;
    transition: 4s;
}

.slider .slider-items .item.active {
    visibility: visible;
    opacity: 1;
    transition: 4s;
}

At least now all of the css is handled within the css and the js purely adds or removes a class name which I feel makes it a bit easier to update.

Answer 2

There are priorities as far as what CSS deems should happen. Take a look at this and let me know if it changes anything for you. If not I'll try and run the code and fix your errors. I want to let you know in advance, I am a pure JS developer. When I need CSS or HTML I create it in JS. I want you to try first, thus it will make you a better developer.

https://www.thebookdesigner.com/2017/02/styling-priorities-css-for-ebooks-3/