<script?type="text/javascript">
??window.onload=function(){
?????var?len1=?getByClass('on','list');
?????alert(len1.length);??//?結(jié)果等于2為正確
var?len2=?getByClass('on');
?????alert(len1.length);??//?結(jié)果等于3為正確
}
function?getByClass(clsName,?parent){
?//定義函數(shù)getByClass()實(shí)現(xiàn)獲取document或指定父元素下所有class為on的元素??
????var?oParent=parent?document.getElementById(parent):document;
????var?arr=new?Array();
????var?oElements=oParent.getElementsByTagName("*");
????for(var?i=0;i<oElements.length;i++){
????????if(oElements[i].className?==??clsName){
????????????arr.push(oElements[i]);
????????}
????}
????return?arr;

????

}
</script>