请如何alert出所单击元素的ID？
<script type="text/javascript">
function justtest() {
alert("Hello"+ );
}
</script>
就是这个单击所响应的函数要怎么写？要求单击某个Label元素的时候能alert出"Hello"+其ID值，现在可以alert出Hello，就是不知道ID要怎么写，求指教谢谢！！
[解决办法]
- HTML code
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html;charset=UTF-8"> <title></title> <script type="text/javascript"> window.onload = function(){ var divs = document.getElementsByTagName('div'); for (var i = divs.length - 1; i >= 0; i--) { divs[i].onclick=justtest; }; } function justtest() { var e = event.srcElement||event.target; alert("Hello:"+e.id ); } </script> </head> <body> <div id="id_1">111</div> <div id="id_2">222</div> <div id="id_3">333</div> <div id="id_4">444</div> </body> </html>