javascript - 循环的 CSS/JS slider 问题

Question

我对 CSS/JS slider 有疑问。我使用简单的方法使其工作 - 较大的元素 (container) 在较小的 (area) 中， overflow hidden 。我在 slider btn 和 btn2 上方有按钮来控制更大元素 (container)

的移动

问题 是它只在到达“第一张幻灯片”(蓝色)之前有效，然后就不可能滑动到第二张幻灯片(红色)。

fiddle :https://jsfiddle.net/26r32hb6

var button = document.querySelector('.btn');
var button2 = document.querySelector('.btn2');
var container = document.querySelector('.container');

button.style.background = 'blue';
button2.style.background = 'blue';
container.style.backgroundColor = 'blue';

button.onclick = function() {  
   if (container.style.left == 0) {  
     container.style.left = '-100.5%';    
     container.style.backgroundColor = 'red';     
     button.style.backgroundColor = 'red';
     button2.style.backgroundColor = 'red';}
else if (container.style.left == '-100.5%') {
  container.style.left = '-200.5%';
  container.style.backgroundColor = 'purple';   
  button.style.backgroundColor = 'purple'; 
  button2.style.backgroundColor = 'purple';    
}
};
button2.onclick = function() {
  if (container.style.left == '-100.5%') { 
    container.style.left = 0; 
    container.style.backgroundColor = 'blue';  
    button.style.backgroundColor = 'blue';
    button2.style.backgroundColor = 'blue';}
  else if (container.style.left == '-200.5%') { 
    container.style.left = '-100.5%';
    container.style.backgroundColor = 'red';      
    button.style.backgroundColor = 'red';
    button2.style.backgroundColor = 'red';
}
};

.wrapbtns {
  width: 365px;
  height: 50px;
  background: yellow;
}
.btn {
  width: 50px;
  height: 50px;
   float: right;
}
.btn2 {
  width: 50px;
  height: 50px;
  float: left;
  margin-right: 5px;
}
.btn, .btn2 {
  transition-duration: 1s;
  display: flex;
  justify-content: center;
  align-items: center;
  color: white;
  cursor: pointer;

}
.area {
  width: 365px;
  height: 250px;
  overflow: hidden; /* This */
  position: relative;
}
.container {
  background: blue;
  width: 1100px;
  height: 250px;
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: left;
  align-items: center;
  left: 0;
  position: absolute;
  transition-duration: 1s;
}
.box {
  background: yellow;
  min-width: 100px;
  height: 100px;
  margin: 1%;
  display: flex;
  justify-content: center;
  align-items: center;
  color: black;
  font-size: 48px;
  transition-duration: 500ms;
}

<div class="wrapbtns">
<div class="btn2">-X</div>
<div class="btn">X</div></div>

<div class="area">
  <div class="container">

    <div class="box">a</div>
    <div class="box">b</div>
    <div class="box">c</div>
    <div class="box">d</div>
    <div class="box">e</div>
    <div class="box">f</div>
    <div class="box">g</div>
    <div class="box">h</div>
    <div class="box">i</div>
    <div class="box">j</div>
    <div class="box">k</div>
    <div class="box">l</div>
    <div class="box">m</div>
    <div class="box">n</div>
    <div class="box">o</div>
    <div class="box">p</div>
    <div class="box">q</div>
    <div class="box">r</div>
  </div>
</div>

Answer 1

首先，如果您使用类似 jQuery 的东西，所有这一切都会变得容易得多.但假设您只想使用 javascript 执行此操作，这是我的解决方案:

(注意:即使您使用 jQuery，该技术也与下面解释的技术非常相似)

fiddle :https://jsfiddle.net/Bintang/kvowcj6w/

var button = document.querySelector('.btn');
var button2 = document.querySelector('.btn2');
var container = document.querySelector('.container');
var area = document.querySelector('.area');

button.style.background = 'blue';
button2.style.background = 'blue';
container.style.backgroundColor = 'blue';

var slideCurrent = 0;
var slideTotal = Math.floor(container.offsetWidth / area.offsetWidth);
var slideWidth = area.offsetWidth;
var slideColors = ['blue', 'red', 'purple'];

button.onclick = function() {

  if (slideCurrent < slideTotal - 1) {
    var left = container.style.left;
    var leftInInteger = parseInt(left.replace("px", "")) || 0;
    container.style.left = (leftInInteger - slideWidth) + "px"
    slideCurrent += 1;

    //STYLING
    container.style.backgroundColor = slideColors[slideCurrent];
    button.style.backgroundColor = slideColors[slideCurrent];
    button2.style.backgroundColor = slideColors[slideCurrent];
  }

};
button2.onclick = function() {

  if (slideCurrent > 0) {
    var left = container.style.left;
    var leftInInteger = parseInt(left.replace("px", "")) || 0;
    container.style.left = (leftInInteger + slideWidth) + "px";
    slideCurrent -= 1;

    //STYLING
    container.style.backgroundColor = slideColors[slideCurrent];
    button.style.backgroundColor = slideColors[slideCurrent];
    button2.style.backgroundColor = slideColors[slideCurrent];
  }

};

解释:

不是每次要滑动时都使用 if & else 来设置“left”的具体值，而是增加每次你想向左滑动时“左”，每次你想向右滑动时递减该值。 (看下面的代码)

var slideCurrent = 0;
var slideTotal = Math.floor(container.offsetWidth / area.offsetWidth);
var slideWidth = area.offsetWidth;
var slideColors = ['blue', 'red', 'purple'];

button.onclick = function() {

  if (slideCurrent < slideTotal - 1) {
    var left = container.style.left;
    var leftInInteger = parseInt(left.replace("px", "")) || 0;
    container.style.left = (leftInInteger - slideWidth) + "px"
    slideCurrent += 1;

    //STYLING
    container.style.backgroundColor = slideColors[slideCurrent];
    button.style.backgroundColor = slideColors[slideCurrent];
    button2.style.backgroundColor = slideColors[slideCurrent];
  }

};
    

上面的代码做了什么:

1.每次点击按钮都会检查当前幻灯片是否是最后一张幻灯片

if (slideCurrent < slideTotal - 1) {

2.如果它不是最后一张幻灯片，它将获取“container”的当前“left”值，然后它将删除“px”并将其从字符串转换为整数(使用 parseInt() 函数)，但如果未定义“left”属性，它将被替换为“0”的值

var left = container.style.left;
var leftInInteger = parseInt(left.replace("px", "")) || 0;

3. 现在它具有整数“left”的当前值，它可以将值减去“区域”(顶部较小的元素)的宽度，因此它将向右滑动并增加 slideCurrent 逐一变化

container.style.left = (leftInInteger - slideWidth) + "px"
slideCurrent += 1;

4.最后，它会将“容器”的颜色设置为指定的颜色

//STYLING
container.style.backgroundColor = slideColors[slideCurrent];
button.style.backgroundColor = slideColors[slideCurrent];
button2.style.backgroundColor = slideColors[slideCurrent];

然后你可以反其道而行之，向另一个方向滑动。