从javascript获取所有uid时出错

Question

In the facebook pokes page ie http://www.facebook.com/pokes I am trying to find all the uid using javascript. From firebug i get the tag name which is following...

<a rel="async-post" ajaxify="/ajax/pokes/poke_inline.php?uid=XXXXXXXXXXXX&amp;pokeback=1" href="#" class="uiIconText"><i style="top: 0px;" class="img sp_1lbo22 sx_3b5b96"></i>Poke Back</a>

To get all the uid, i designed my javascript in following manner-

var allAnchorElements = document.getElementsByTagName('a');

for (var i = 0; i < allAnchorElements.length; i++) {
   var uid = allAnchorElements[i].ajaxify.match(/uid=([0-9]*)/)[1];

I haven't put the complete code here. Now when executing this code from firebug console, i am getting TypeError: allAnchorElements[i].ajaxify is undefined error.

Why i am getting this error? How can i change my script to get all uid?

Answer 1

Well document.getElementsByTagName('a'); is getting all of the links on the page. Do all of the links have that attribute? If the answer is no, filter them out.

One way:

var allAnchorElements = document.getElementsByTagName('a');
for (var i = 0; i < allAnchorElements.length; i++) {
    var ajaxify = allAnchorElements[i].ajaxify;
    if (!ajaxify) {
        continue;
    }
    var uid = ajaxify.match(/uid=([0-9]*)/)[1];
}

Another way would be to use a querySelector to get the elements.