javascript通过class来获取元素实现代码

function getByClass(classname){ 
var nodes = document.getElementsByTagName('*'), 
ret=[]; 
for(var i=0;i<nodes.length;i++){ 
if(hasClass(nodes[i],classname)) 
ret.push(nodes[i]); 
} 
return ret; 
} 
function hasClass(node,className){ 
var names = node.className.split(/\s+/); 
for(var i=0;i<names.length;i++){ 
if(names[i]==className) 
return true; 
}return false; 
}