javascript根据class获取元素

/*
Written by Jonathan Snook, http://www.snook.ca/jonathan Add-ons by Robert Nyman, http://www.robertnyman.com Author says "The credit comment is all it takes, no license. Go crazy with it!:-)"
From http://www.robertnyman.com/2005/11/07/the-ultimate-getelementsbyclassname/ */
function getElementsByClassName(oElm, strTagName, oClassNames){
var arrReturnElements = new Array();
if ( typeof( oElm.getElementsByClassName ) == "function" ) {
/* Use a native implementation where possible FF3, Saf3.2, Opera 9.5 */
var arrNativeReturn = oElm.getElementsByClassName( oClassNames );
if ( strTagName == "*" )
return arrNativeReturn;
for ( var h=0; h < arrNativeReturn.length; h++ ) {
if( arrNativeReturn[h].tagName.toLowerCase() == strTagName.toLowerCase() )
arrReturnElements[arrReturnElements.length] = arrNativeReturn[h];
}
return arrReturnElements;
}
var arrElements = (strTagName == "*" && oElm.all)? oElm.all : oElm.getElementsByTagName(strTagName);
var arrRegExpClassNames = new Array();
if(typeof oClassNames == "object"){
for(var i=0; i<oClassNames.length; i++){
arrRegExpClassNames[arrRegExpClassNames.length] =
new RegExp("(^|\\s)" + oClassNames[i].replace(/\-/g, "\\-") + "(\\s|$)");
}
}
else{
arrRegExpClassNames[arrRegExpClassNames.length] =
new RegExp("(^|\\s)" + oClassNames.replace(/\-/g, "\\-") + "(\\s|$)");
}
var oElement;
var bMatchesAll;
for(var j=0; j<arrElements.length; j++){
oElement = arrElements[j];
bMatchesAll = true;
for(var k=0; k<arrRegExpClassNames.length; k++){
if(!arrRegExpClassNames[k].test(oElement.className)){
bMatchesAll = false;
break;
}
}
if(bMatchesAll){
arrReturnElements[arrReturnElements.length] = oElement;
}
}
return (arrReturnElements)
}