javascript元素内容渐现效果代码实例

快乐打工仔 分类:实例代码

本章节分享一段代码实例,他实现了元素的渐现效果。

代码实例如下:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.pipipi.net/" />
<title>犀牛前端部落</title>
<style>
*{
  margin:5px;
}
body, ul, li{
  margin:0;
  padding:0;
  font:12px/1.5 arial;
}
#list{
  width:400px;
}
#list li{
  list-style:none;
  padding:5px 0;
  overflow:hidden;
  border-bottom:1px dotted #ccc;
  filter:alpha(opacity:0);
  opacity:0;
  vertical-align: middle;
}
</style>
<script>
window.onload = function(){
  var btn = document.getElementById("btn");
  var con = document.getElementById("con");
  var list = document.getElementById("list");
  var list_li = list.getElementsByTagName("li");
  btn.onclick = function(){
    var li = document.createElement("li");
    li.innerHTML = con.value;
    con.value='';
    if(list_li.length>=1){
      list.insertBefore(li,list_li[0]);
    }
    else{
      list.appendChild(li);
    }
    var height=li.offsetHeight;
    li.style.height='0';
    startrun(li,"height",height,function(){
      startrun(li,"opacity","100");
    })
  }
}
function getstyle(obj,name){
  if(obj.currentStyle){
    return obj.currentStyle[name];
  }
  else{
    return getComputedStyle(obj,false)[name];
  }
}
function startrun(obj,attr,target,fn){
  clearInterval(obj.timer);
  obj.timer = setInterval(function(){
    var cur = 0;
    if(attr == "opacity"){
      cur = Math.round(parseFloat(getstyle(obj,attr))*100);
    }
    else{
      cur = parseInt(getstyle(obj,attr));
    }
    var speed = (target-cur)/8;
    speed = speed>0?Math.ceil(speed):Math.floor(speed);
    if(cur == target){
      clearInterval(obj.timer);
      if(fn){
        fn();
      }
    }
    else{
      if(attr == "opacity"){
        obj.style.filter = "alpha(opacity="+(cur+speed)+")";
        obj.style.opacity = (cur+speed)/100;
      }
      else{
        obj.style = cur + speed + "px";
      }
    }
  },30)
}
</script>
</head>
<body>
<textarea id="con" cols="50" rows="5"></textarea>
<input id="btn" name="" type="button" value="发布">
<ul id="list"></ul>
</body>
</html>

在多行文本框输入内容,然后点击按钮之后,就可以看到文档内容的渐现效果。

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