封装函数

//通过类名获取元素

//name为class名，obj为搜索的对象

function getByClass(obj,name){

if(document.getElementsByClassName){
return obj.getElementsByClassName(name);
}
else{
var aStr = obj.getElementsByTagName('*');

var arr = []
for(var i=0; i<aStr.length; i++){
var str = aStr[i].className;
var arr1 = str.split(' ');
for (var j=0; j<arr1.length; j++) {
if(arr1[j]==name){
arr.push(aStr[i]);
}
}
}
return arr;

}

}