Posted in Javascript onApril 10, 2015
本文实例讲述了js实现类似新浪微博首页内容渐显效果的方法。分享给大家供大家参考。具体分析如下:
要点一:
if(list_li.length>=1){ list.insertBefore(li,list_li[0]); }else{ list.appendChild(li); }
从在前面插入新内容,如果没有新内容,就是在后面插入新内容。
要点二:
var height=li.offsetHeight; li.style.height='0';
取得li的高度,然后再li的高度设置为0,因为高度的变化是从0到现有高度。
要点三:
startrun(li,"height",height,function(){ startrun(li,"opacity","100"); })
先是高度变化,再是透明度变化
最后,上代码:
<!DOCTYPE html> <html> <head> <meta charset="gb2312" /> <title>无标题文档</title> <style> <!-- body,ul,li{margin:0; padding:0; font:12px/1.5 arial;} #list{width:400px; margin:10px auto;} #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[attr] = 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>
希望本文所述对大家的javascript程序设计有所帮助。
js实现类似新浪微博首页内容渐显效果的方法
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jingangel声明:登载此文出于传递更多信息之目的,并不意味着赞同其观点或证实其描述。
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