Js_dom_02

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通过Js创建dom节点比如发送邮件时的添加附件届时通过添加dom节点完成的

createElement(标签名) 创建一个节点 appendChild(节点) 追加一个节点

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style></style><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script type="text/javascript">window.onload=function (){var oBtn=document.getElementById('btn1');var oTxt=document.getElementById('txt1');var oUl=document.getElementById('ul1');oBtn.onclick=function (){var oLi=document.createElement('li');oLi.innerHTML=oTxt.value;//父.appendChild(子节点)oUl.appendChild(oLi);}}</script></head><body><input id="txt1" type="text" /><input id="btn1" type="button" value="创建Li"/><ul id="ul1"><li>aaa</li></ul></body></html>

insertBefore 可以指定在某个节点之前插入自己创建的节点比如发送微博时新插入的节点显示在第一条

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style></style><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script type="text/javascript">//父.insertBefore(子节点, 谁之前)window.onload=function (){var oBtn=document.getElementById('btn1');var oTxt=document.getElementById('txt1');var oUl=document.getElementById('ul1');oBtn.onclick=function (){var oLi=document.createElement('li');var aLi=oUl.getElementsByTagName('li');oLi.innerHTML=oTxt.value;if(aLi.length==0){oUl.appendChild(oLi);}else{oUl.insertBefore(oLi, aLi[0]);}}}</script></head><body><input id="txt1" type="text" /><input id="btn1" type="button" value="创建Li"/><ul id="ul1"></ul></body></html>

removeChild(节点) 删除一个节点

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style></style><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script type="text/javascript">window.onload=function (){var aA=document.getElementsByTagName('a');var oUl=document.getElementById('ul1');var i=0;for(i=0;i<aA.length;i++){aA[i].onclick=function (){oUl.removeChild(this.parentNode);}}}</script></head><body><ul id="ul1"><li>sdfsdf <a href="javascript:;">删除</a></li><li>3432 <a href="javascript:;">删除</a></li><li>tttt <a href="javascript:;">删除</a></li><li>ww <a href="javascript:;">删除</a></li></ul></body></html>

文档碎片一种理论上可以提高性能的方案但是实际上并没有

文档碎片的原理 :

比如要添加1W个节点到ul节点下正常的做法是createElement 然后 appendChild 如此循环1W次但是

文档碎片的做法是createDocumentFragment
创建出来的1W个节点先存起来然后一次性appendChild

比较以下两个案例

普通的添加

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style></style><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script type="text/javascript">window.onload=function (){var oBtn=document.getElementById('btn1');var oUl=document.getElementById('ul1');oBtn.onclick=function (){var iStart=new Date().getTime();var i=0;for(i=0;i<100000;i++){var oLi=document.createElement('li');oUl.appendChild(oLi);}alert(new Date().getTime()-iStart);}}</script></head><body><input id="btn1" type="button" value="普通"/><ul id="ul1"></ul></body></html>

文档碎片的方式添加

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style></style><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script type="text/javascript">window.onload=function (){var oBtn=document.getElementById('btn1');var oUl=document.getElementById('ul1');oBtn.onclick=function (){var iStart=new Date().getTime();var oFrag=document.createDocumentFragment();var i=0;for(i=0;i<100000;i++){var oLi=document.createElement('li');oFrag.appendChild(oLi);}oUl.appendChild(oFrag);alert(new Date().getTime()-iStart);}}</script></head><body><input id="btn1" type="button" value="碎片"/><ul id="ul1"></ul></body></html>

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