[JS+CSS3] Sample code to implement slideshow effect with preview_javascript skills

<script type="text/javascript">

  // 1、数据定义（实际生产环境，应由后台给出）
  var data = [
    {img:1,h2:"我是标题二,小标题",h3:"我是标题三,大标题"},
    {img:2,h2:"我是标题二,小标题",h3:"我是标题三,大标题"},
    {img:3,h2:"我是标题二,小标题",h3:"我是标题三,大标题"},
    {img:4,h2:"我是标题二,小标题",h3:"我是标题三,大标题"},
    {img:5,h2:"我是标题二,小标题",h3:"我是标题三,大标题"},
    {img:6,h2:"我是标题二,小标题",h3:"我是标题三,大标题"},
    {img:7,h2:"我是标题二,小标题",h3:"我是标题三,大标题"},
  ];

  // 2、通用函数
  var g = function(id){
    if( id.substr(0,1) =="." ){
      return document.getElementsByClassName( id.substr(1) );
    }
    return document.getElementById(id);
  }

  // 3、添加幻灯片的操作（所有幻灯片&对应的按钮）
  function addSliders(){
    // 3.1 获取模版
    var tpl_main = g("template_main").innerHTML
      .replace(/^\s*/,'')
      .replace(/\s*$/,'');

    var tpl_ctrl = g("template_ctrl").innerHTML
      .replace(/^\s*/,'')
      .replace(/\s*$/,'');

    // 3.2 定义最终输出HTML的变量
    var out_main = [];
    var out_ctrl = [];

    // 3.3 遍历所有数据，构建最终输出的HTML
    for( i in data ){
      var _html_main = tpl_main
        .replace(/{{index}}/g,data[i].img)
        .replace(/{{h2}}/g,data[i].h2)
        .replace(/{{h3}}/g,data[i].h3)
        .replace(/{{css}}/g,['','main_i_right'][i%2]);

      var _html_ctrl = tpl_ctrl
        .replace(/{{index}}/g,data[i].img);
      
      out_main.push(_html_main);
      out_ctrl.push(_html_ctrl);
    }

    // 3.4 把HTML回写到对应的DOM里面
    g("template_main").innerHTML = out_main.join('');
    g("template_ctrl").innerHTML = out_ctrl.join('');
    
    // 7、增加#main_background
    g('template_main').innerHTML += tpl_main
      .replace(/{{index}}/g,'{{index}}')
      .replace(/{{h2}}/g,data[i].h2)
      .replace(/{{h3}}/g,data[i].h3);

    g('main_{{index}}').id = 'main_background';
  }

  // 5、幻灯片切换
  function switchSliders(n){
    // 5.1 获得要展现的幻灯片&控制按钮 DOM
    var main = g("main_"+n);
    var ctrl = g("ctrl_"+n);

    // 5.2 获得所有的幻灯片&控制按钮
    var clear_main = g('.main_i');
    var clear_ctrl = g('.ctrl_i');

    // 5.3 清除他们的active样式
    for(var i=0;i<clear_ctrl.length;i++){
      clear_main[i].className = clear_main[i].className.replace('main_i_active','');
      clear_ctrl[i].className = clear_ctrl[i].className.replace('ctrl_i_active','');
    }

    // 5.4为当前控制按钮和幻灯片附加样式  
    g("main_"+n).className += ' main_i_active';
    g("ctrl_"+n).className += ' ctrl_i_active';
    // 7.2切换时 复制上一张幻灯片到main_background中
    setTimeout(function(){
      g('main_background').innerHTML = main.innerHTML;
    },1000);
    
  }

  // 6、动态调整图片的margin-top 使其垂直居中
  function movePictures(){
    var pictures = g('.picture');
    for(i=0;i<pictures.length;i++){
      pictures[i].style.marginTop = -(pictures[i].clientHeight/3) + 'px';
    }
  }

  // 4、定义何时处理幻灯片输出
  window.onload = function(){
    addSliders();
    switchSliders(1);
    setTimeout(function(){
      movePictures();
    },100)
  }
</script>