JavaScript 实现 getElementsByClassName 方法及使用示例

function getElementsByClassName(n) {
var classElements = [], allElements = document.getElementsByTagName('*');
for (var i=0; i< allElements.length; i++ )
{ 
if (allElements[i].className == n ) {
classElements[classElements.length] = allElements[i];
} 
} 
return classElements;
}
var redClassElements = getElementsByClassName('aa'); 
for (var i=0; i<redClassElements.length; i++) { 
 //do something
}