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js實作類別似新浪微博首頁內容漸顯效果的方法，首頁內容漸顯
本文執行個體講述了js實作類別似新浪微博首頁內容漸顯效果的方法。分享給大家供大家參考。具體分析如下：
要點一：
if(list_li.length>=1){list.insertBefore(li,list_li[0]);}else{list.appendChild(li);}
從在前面插入新內容，如果沒有新內容，就是在後面插入新內容。
要點二：
var height=li.offsetHeight;li.style.height='0';
取得li的高度，然後再li的高度設定為0,因為高度的變化是從0到現有高度。
要點三：
startrun(li,"height",height,function(){startrun(li,"opacity","100");})
先是高度變化，再是透明度變化
最後，上代碼：
<!DOCTYPE html><html><head><meta charset="gb2312" /><title>無標題文檔</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="發布"><ul id="list"></ul></body></html>
希望本文所述對大家的javascript程式設計有所協助。
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