Bootstrap轮播使文本逐个字母出现

Question

我正在使用引导轮播作为滑块，在每张幻灯片上都有一些文字。

我希望幻灯片上的文字一个字母一个字母地出现。

我几乎解决了..

但是有两个问题

1. 在第一张幻灯片上，文本根本没有出现
2. 如果用户转到浏览器上的某个其他选项卡意味着如果当前窗口不在焦点上，那么一切都会搞砸。

Here is my fiddle

HTML

<main>
      <div class="container">
        <div class="block-wrap">
          <div id="js-carousel" class="carousel slide" data-ride="carousel">
            <!-- Wrapper for slides -->
            <div class="carousel-inner" role="listbox">
              <div class="item active">
                <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Chania">
                <div class="caption">

                  <div class="mystring hide">companies with Inbound Marketing</div>
                  <h4>We help <div class="demo-txt"></div> </h4>
                </div>
              </div>

              <div class="item">
                <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Chania">
                <div class="caption">
                <div class="mystring hide">companies with Inbound Marketing</div>

                  <h4>We help  <div class="demo-txt "></div> </h4>
                </div>
              </div>

              <div class="item">
                <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Flower">
                <div class="caption">
                <div class="mystring hide">2companies with Inbound Marketing</div>

                  <h4>We help <div class="demo-txt"></div> </h4>
                </div>
              </div>

              <div class="item">
                <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Flower">
                <div class="caption">
                <div class="mystring hide">3companies with Inbound Marketing</div>

                  <h4>We help <div class="demo-txt"></div> </h4>
                </div>
              </div>
              <div class="overlay-effect"></div>
            </div>
          </div>
        </div> 
      </div>
    </main>

JS：

$(document).ready(function() {    
     $('#js-carousel').carousel({
        interval: 5000
    });

     $('#js-carousel').on('slid.bs.carousel', function () {
      var showText = function (target, message, index, interval) { 
        if (index < message.length) { 
          $(target).append(message[index++]); 
          setTimeout(function () { showText(target, message, index, interval); }, interval); 
        } 
      }                 
       var str = $(this).find(".active .mystring").html();
          $('.active .demo-txt').html("");         
          showText(".active .demo-txt", str, 0, 100);          
     });
    });

Answer 1

使用setInterval 函数代替settimeout。还可以使用clearInterval 在新幻灯片开始时清除计划。 （我认为这是你的第二个问题。）

这是你的目标 js 文件：

$(document).ready(function() {    
    $('#js-carousel').carousel({
        interval: 5000
    });
    var handler;
    var interval = 5000;
    var index = 0;
    function showText(target, message, index, interval) { 
        if (index < message.length) { 
            $(target).append(message[index]); 
        }
    }

    function iteration() {
        if(handler){
            clearInterval(handler);
        }
        index = 0;
        var str = $(this).find(".active .mystring").html();
        $('.active .demo-txt').html("");
        showText(".active .demo-txt", str, index++, 100);         
        handler = setInterval(function(){
            showText(".active .demo-txt", str, index++, 100);
        }, 100);
     }

     //on each carousel slide change: 
     $('#js-carousel').on('slid.bs.carousel', iteration);
     //start immediately for your first problem:
     iteration.bind($('#js-carousel'))();
});

Answer 2

这是因为你的函数在幻灯片事件中。开始时，轮播不滑动...

小提琴：https://jsfiddle.net/Lbasa2jh/5/

JS：

$(document).ready(function() {  
    var showText = function (target, message, index, interval) { 
    if (index < message.length) { 
          $(target).append(message[index++]); 
          setTimeout(function () { showText(target, message, index, interval); }, interval); 
        } 
      };

    $('#js-carousel').carousel({
        interval: 5000
    });

       var str0 = $(this).find(".active .mystring").html();
       $('.active .demo-txt').html("");         
       showText(".active .demo-txt", str0, 0, 100);    

     $('#js-carousel').on('slid.bs.carousel', function () {

       var str = $(this).find(".active .mystring").html();
          $('.active .demo-txt').html("");         
          showText(".active .demo-txt", str, 0, 100);          
     });
    });

Answer 3

The timer can be tricky when the tab goes inactive.我移动了代码并清除了超时，以确保在开始新幻灯片时超时是干净的。

当从不同的标签切换回来时，我注意到一个问题（并非总是如此），即轮播实际上移动到下一张幻灯片的速度快于 5 秒，导致文本不完整。

https://jsfiddle.net/vLwm58Ln/

$(document).ready(function() {
  $('#js-carousel').carousel({
    interval: 5000
  });

  var showText = function(target, message, index, interval) {
    if (index < message.length) {      
      	$(target).append(message[index++]);
        timer = setTimeout(function() {
           showText(target, message, index, interval);
        }, interval);
    }
  }, timer;
  
  //First time, this triggers right away instead of waiting for the slide to move
  showText(".active .demo-txt", $('#js-carousel').find(".active .mystring").html(), 0, 100);
  
  $('#js-carousel').on('slid.bs.carousel', function() {
    //clear any messed up timeout from prev slide
    clearTimeout(timer);
    //clear message that may be incomplete from the previous text animation
    $('.prevActive').removeClass('prevActive').html('');
    var str = $(this).find(".active .mystring").html();
    $('.active .demo-txt').addClass('prevActive').html("");
	showText(".active .demo-txt", str, 0, 100);
  });
});

.carousel-inner {
  position: relative;
}

.carousel-inner .overlay-effect {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.6);
}

.carousel-inner .caption {
  color: #ffffff;
  font-weight: bold;
  position: absolute;
  top: 0;
  bottom: 0;
  margin: auto 0;
  height: 100px;
  z-index: 9999;
  left: 5%;
}

.carousel-inner .caption h1,
.carousel-inner .caption h2 {
  font-weight: bold;
  line-height: 1.6;
}

.carousel-inner .caption h1 {
  font-size: 64px;
}

.carousel-inner .caption h2 {
  font-size: 44px;
}

.carousel-inner .demo-txt {
  border-bottom: 4px solid #ec8422;
  padding-bottom: 5px;
}

<script type="text/javascript" src="https://code.jquery.com/jquery-1.11.2.js"></script>
<script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<link rel="stylesheet" type="text/css" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<main>
  <div class="container">
    <div class="block-wrap">
      <div id="js-carousel" class="carousel slide" data-ride="carousel">
        <!-- Wrapper for slides -->
        <div class="carousel-inner" role="listbox">
          <div class="item active">
            <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Chania">
            <div class="caption">

              <div class="mystring hide">companies with Inbound Marketing</div>
              <h4>We help <div class="demo-txt"></div> </h4>
            </div>
          </div>

          <div class="item">
            <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Chania">
            <div class="caption">
              <div class="mystring hide">companies with Inbound Marketing</div>

              <h4>We help  <div class="demo-txt "></div> </h4>
            </div>
          </div>

          <div class="item">
            <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Flower">
            <div class="caption">
              <div class="mystring hide">2companies with Inbound Marketing</div>

              <h4>We help <div class="demo-txt"></div> </h4>
            </div>
          </div>

          <div class="item">
            <img src="http://cdn.theatlantic.com/assets/media/img/photo/2015/11/images-from-the-2016-sony-world-pho/s01_130921474920553591/main_900.jpg?1448476701" alt="Flower">
            <div class="caption">
              <div class="mystring hide">3companies with Inbound Marketing</div>

              <h4>We help <div class="demo-txt"></div> </h4>
            </div>
          </div>
          <div class="overlay-effect"></div>
        </div>
      </div>
    </div>
  </div>
</main>