javascript - 创建淡出/淡入而不是显示无/阻止

Question

我正在尝试使用 JS 使幻灯片淡入和淡出，而不是显示无/ block 。这是否需要使用 css 来完成，或者我可以只用 JS 来完成吗？谢谢

代码:

var slideIndex = 1;
showSlides(slideIndex);

function plusSlides(n) {
  showSlides(slideIndex += n);
}

function currentDot(n) {
  showSlides(slideIndex = n);
}

function showSlides(n) {
    console.log('SHOWSLIDES');
      var i;
      var slides = document.getElementsByClassName("mySlides");
      var dots = document.getElementsByClassName("nav-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";
}

或者将其转换为 jquery 并使用 .fadeOut()/.fadeIn() 会更好

Answer 1

之前:稍微了解一下 jQuery 的源代码:

1. .fadeIn()

http://james.padolsey.com/jquery/#v=1.11.2&fn=fadeIn

.animation()

http://james.padolsey.com/jquery/#v=1.11.2&fn=animate

这是一种可行的方法:

var fadeInBtn = document.getElementById('fadeIn');
fadeInBtn.addEventListener('click', function() {
  var testString = document.getElementById('test');
  fadeIn(testString, 30);
});

var fadeOutBtn = document.getElementById('fadeOut');
fadeOutBtn.addEventListener('click', function() {
  var testString = document.getElementById('test');
  fadeOut(testString, 60);
});



function fadeIn(element, speed) {
  var interval = setInterval(function () {
    
    var opacity = parseFloat(element.style.opacity);
    if(opacity >= 1.0) {
       clearInterval(interval);
    }

    element.style.opacity = opacity + 0.1;
  }, speed);
};

function fadeOut(element, speed) {
  var interval = setInterval(function () {
    
    var opacity = parseFloat(element.style.opacity);
    if(opacity <= 0) {
       clearInterval(interval);
    }

    element.style.opacity = opacity - 0.1;
  }, speed);
}

div {
  font-size: 300%;
}

<button id="fadeIn">Test .fadeIn()</button>
<button id="fadeOut">Test .fadeOut()</button>
<div id="test" style="opacity: 0">Example String</div>

另一个解决方案是使用 CSS(3)。我在这里引用这个已经提出的问题:Using CSS for fade-in effect on page load