一些常用的JS功能函数代码

//获取对象 
function getObject(objectId,top) 
{ 
doc = top?window.top.document:document; 
if(typeof(objectId)!="object" && typeof(objectId)!="function") 
{ 
if(doc.getElementById && doc.getElementById(objectId)) 
{ 
// W3C DOM 
return doc.getElementById(objectId); 
} 
else if(doc.getElementsByName(objectId)) 
{ 
return doc.getElementsByName(objectId)[0]; 
} 
else if (doc.all && doc.all(objectId)) 
{ 
// MSIE 4 DOM 
return doc.all(objectId); 
} 
else if (doc.layers && doc.layers[objectId]) 
{ 
// NN 4 DOM.. note: this won't find nested layers 
return doc.layers[objectId]; 
} 
else 
{ 
return false; 
} 
}else 
return objectId; 
} 
//获取相对路径 
function getRelativePath() 
{ 
var url = location.href;//当前url 
var urlcs = String(location.search); 
url = url.replace(urlcs,""); 
var path = url.length - url.replace(/\//g,"").length - 3; //层次为url包含/的长度-没有包含/的长度再减去项目头/的个数 var str = ""; 
for(var i = 0; i < path; i++) 
{ 
str += "../";//组合成一个相对路径的字符串返回 
} 
return str; 
} 
//加载其他JS文件或CSS文件 
function loadjscssfile(filename,filetype,chkonce) 
{ 
filetype = !filetype?"js":filetype; 
var had = false; 
if(filetype=="js") 
{ 
if(chkonce) 
{ 
var allScripts = document.getElementsByTagName("script"); 
for(var i=0;i<allScripts.length;i++) 
{ 
try{ 
if(allScripts[i].src.indexOf(filename)>-1) 
{ 
had = true; 
break; 
} 
}catch(e){} 
} 
} 
if(!had) 
{ 
document.write("<script src=""+filename+"" src=""+filename+"" type='text/javascript'></script>"); 
} 
}else 
{ 
if(chkonce) 
{ 
var allCss = document.getElementsByTagName("link"); 
if(allCss.length) 
{ 
for(var i=0;i<allCss.length;i++) 
{ 
try{ 
if(allCss[i].href.indexOf(filename)>-1) 
{ 
had = true; 
break; 
} 
}catch(e){} 
} 
} 
} 
if(!had) 
{ 
document.write("<link type='text/css' rel='stylesheet' href=""+filename+"" href=""+filename+"" />"); 
} 
} 
} 
//定义根目录路径 
var ROOT_PATH = getRelativePath(); 
var JS_PATH = ROOT_PATH+'js/'; 
var AJAX_PATH = ROOT_PATH+'ajax/'; 
var CSS_PATH = ROOT_PATH+'css/'; 
var IMAGES_PATH = ROOT_PATH+'images/'; 
var EDITOR_PATH = ROOT_PATH+'uploadeditor/'; 
var PUB_PATH = ROOT_PATH+'uploadfile/'; 
//加载公共变量的JS 
loadjscssfile(JS_PATH+"globalPara.js"); 
//设置下拉表中某一项被选中 
function setSelOption(objId,vlu) 
{ 
objId = getObject(objId); 
for(var i=0;i<objId.options.length;i++) 
{ 
if(objId.options[i].value==vlu) 
{ 
objId.options[i].setAttribute("selected","selected"); 
break; 
} 
} 
} 
//根据下拉表中的option文本设置某一项被选中 
function setTxtOption(objId,txt) 
{ 
objId = getObject(objId); 
for(var i=0;i<objId.options.length;i++) 
{ 
if(objId.options[i].innerHTML==txt) 
{ 
objId.options[i].setAttribute("selected","selected"); 
break; 
} 
} 
} 
//设置单选按钮组中某一项被选中 
function setSelRadio(objName,vlu) 
{ 
objName = document.getElementsByName(objName); 
for(var i=0;i<objName.length;i++) 
{ 
if(objName[i].value==vlu) 
{ 
objName[i].setAttribute("checked","checked"); 
break; 
} 
} 
} 
//根据ID设置复选框中某些项被选中 
//vlu 的格式为 ： 1,2,3 
function setSelCheckbox(prefix,vlu) 
{ 
var _arr = vlu.split(","); 
if(_arr!="") 
{ 
for(var i=0; i<_arr.length; i++) 
{ 
getObject(prefix+_arr[i]).checked = true; 
} 
} 
} 
//快捷输入，fromObj：来源对象，toObjId：目标对象的ID，txt为true时取toObjId的innerHTML值 
function fastInput(fromObj,toObjId,txt) 
{ 
if(fromObj.value=='' || fromObj.value==0) return false; 
txt = !txt ? false : txt; 
var toObj = getObject(toObjId); 
if(txt) 
{ 
if(typeof (toObj.value) == 'undefined') 
toObj.innerHTML = toTxt(fromObj.options[fromObj.selectedIndex].innerHTML); 
else 
toObj.value = toTxt(fromObj.options[fromObj.selectedIndex].innerHTML); 
}else 
{ 
if(typeof (toObj.value) == 'undefined') 
toObj.innerHTML = fromObj.value; 
else 
toObj.value = fromObj.value; 
} 
} 
/* 
IE6,IE7上传图片前预览图片 
IE6下还可以同时检测图片的大小 
size 单位为KB 
<style type="text/css"><!-- 
.newPreview 
{ 
width:400px; height:300px; 
FILTER: progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale) 
} 
.nodis{display:none;} 
--></style><style type="text/css" bogus="1"> 
.newPreview 
{ 
width:400px; height:300px; 
FILTER: progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale) 
} 
.nodis{display:none;}</style> 
<input type="file" name="litpic" onchange="PreviewImg(this,'newPreview','ndsPreview',400)" /> 
<div id="newPreview" class="newPreview"></div> 
<img id="ndsPreview" class="nodis" /> 
*/ 
function PreviewImg(imgFile,newPreview,ndsPreview,size) 
{ 
newPreview = getObject(newPreview); 
if(!imgFile || !imgFile.value || !newPreview){return}; 
var patn = /\.jpg$|\.jpeg$|\.gif$|\.png$|\.bmp$/i; 
if(patn.test(imgFile.value)) 
{ 
try{newPreview.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgFile.value;}catch(e){} 
if(navigator.appVersion.indexOf("MSIE 6.0",0)>-1) 
{ 
size=!size?0:size; 
ndsPreview = getObject(ndsPreview); 
if(ndsPreview) 
{ 
try{ndsPreview.attachEvent("onreadystatechange", function(){checkImgSize(ndsPreview,size)})}catch(e){} 
ndsPreview.src = imgFile.value; 
} 
} 
} 
else 
{ 
alert("您选择的不是图像文件,请重新选择."); 
} 
} 
function PreviewImgNow(imgDiv,imgFile) 
{ 
try{getObject(imgDiv).filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgFile}catch(e){} 
} 
//上传之前检测图片的大小 
//条件是在file改变时要触发函数将缩略图显示在img上 
//size 单位为KB 
function checkImgSize(img,size) 
{ 
img = getObject(img); 
if(img.readyState == "complete") 
{ 
var limit = size * 1024; 
if(img.fileSize > limit) 
{ 
alert("出错！您上传的图片大小为"+(parseInt(img.fileSize/1024))+"KB,超过了"+size+"KB的限制，请重新上传"); 
return false 
}else 
return true; 
} 
return true; 
} 
//检测客户端环境 
function ClientMentInfo() 
{ 
var me = this; 
var appVer = navigator.userAgent; 
this.GetBrowserName = function (){ 
if(appVer.indexOf("MSIE")>0) return "IE"; 
else if(appVer.indexOf("Firefox")>0) return "Firefox"; 
else if(appVer.indexOf("Chrome")>0) return "Chrome"; 
else if(appVer.indexOf("Safari")>0) return "Safari"; 
else if(appVer.indexOf("Camino")>0) return "Camino"; 
else if(appVer.indexOf("Konqueror")>0) return "Konqueror"; 
else return "其它"; 
} 
this.GetOSInfo = function (){ 
var _pf = navigator.platform; 
if(_pf == "Win32" || _pf == "Windows") 
{ 
if(appVer.indexOf("Windows NT 6.0") > -1 || appVer.indexOf("Windows Vista") > -1) 
{ 
return 'Windows Vista'; 
}else if(appVer.indexOf("Windows NT 6.1") > -1 || appVer.indexOf("Windows 7") > -1) 
{ 
return 'Windows 7'; 
}else 
{ 
try{ 
var _winName = Array('2000','XP','2003'); 
var _ntNum = appVer.match(/Windows NT 5.\d/i).toString(); 
return 'Windows ' + _winName[_ntNum.replace(/Windows NT 5.(\d)/i,"$1")]; 
}catch(e){return 'Windows';} 
} 
}else if(_pf == "Mac68K" || _pf == "MacPPC" || _pf == "Macintosh") 
{ 
return "Mac"; 
}else if(_pf == "X11") 
{ 
return "Unix"; 
}else if(String(_pf).indexOf("Linux") > -1) 
{ 
return "Linux"; 
}else 
{ 
return "Unknow"; 
} 
} 
this.OS = me.GetOSInfo(); //操作系统类型 
this.IeVer = null; 
this.Bs_lang = (navigator.appName == 'Netscape'?navigator.language:navigator.browserLanguage);//浏览器语言版本 
this.Bs_Name = me.GetBrowserName(); //浏览器名称 
//浏览器版本 
if(this.Bs_Name=='IE') 
{ 
var _msie = appVer.match(/MSIE \d./i).toString(); 
this.Bs_Version = this.IeVer = _msie.replace(/MSIE (\d)./i,"$1"); 
}else 
{ 
this.Bs_Version = appVer; 
} 
this.Ie6 = this.IeVer==6 ? true: false; 
this.Ie7 = this.IeVer==7 ? true: false; 
this.Ie8 = this.IeVer==8 ? true: false; 
} 
//客户端信息 
var CMInfo = new ClientMentInfo(); 
//IE6 下缓存背景图片 
if(CMInfo.Ie6) 
{ 
document.execCommand("BackgroundImageCache", false, true); 
} 
//设置复选框全选或全不选 
function setAllCheckbox(formName,objName,num) 
{ 
if(formName) 
_arr = getObject(formName).elements[objName]; 
else 
_arr = typeof(objName)=="object"?objName:document.all(objName); 
if(_arr) 
{ 
if(num) 
{ 
if (!_arr.length ) // 只有一个复选框，则length = undefined 
_arr.checked = true; 
else 
{ 
for(var i=0; i<_arr.length; i++) 
{ 
_arr[i].checked = true; 
} 
} 
}else 
{ 
if (!_arr.length ) // 只有一个复选框，则length = undefined 
_arr.checked = false; 
else 
{ 
for(var i=0; i<_arr.length; i++) 
{ 
_arr[i].checked = false; 
} 
} 
} 
} 
} 
//使当前页面跳到指定的页数页面 
function goPage(pageNum,pageStr) 
{ 
window.location.href = "?np="+pageNum+pageStr; 
} 
//分别去字符串前后，左边，右边空格 
String.prototype.trim = function(){ return this.replace(/^\s+|\s+$/g,"")} 
String.prototype.ltrim = function(){ return this.replace(/^\s+/g,"")} 
String.prototype.rtrim = function(){ return this.replace(/\s+$/g,"")} 

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/linyuanxing/archive/2008/12/01/3421058.aspx

注意globalPara.js本作者常用到的一些每个站自己的常用变量和常量的文件，如果你不需要这样的文件，可把
//加载公共变量的JS
loadjscssfile(JS_PATH+"globalPara.js");
这两句删掉，不然会报错。
（2009-06-04更新）
将 ClientMentInfo类改成了兼容IE6,IE7,IE8,Vista,Windows 7和Firefox