I need help with selecting a DOM node

[narutodude000]

<a class="lbcontainer" onclick="linkbuttonajax('http://example.com',1,true);return false;"><span class="lbbutton"></span><span class="lbcount"><button type="button" class="lbnum" name="num">1</button></span></a>

linkbuttonajax() changes the value of the button. However, I'm having trouble selecting the button. I tried the following, and many other methods:

this.getElementsByTagName('button').innerText
this.lastchild.num.innerText
this.num.childNodes[1].childNodes[0].innerText

However, none of these work.

[Fang]

this.getElementsByTagName('button')[0].firstChild.data

[narutodude000]

I'm getting this error: Uncaught TypeError: Object [object DOMWindow] has no method 'getElementsByTagName'

The page with the button is here: http://linksku.com
The buttons are the blue ones near the center of the page.

[narutodude000]

I need urgent help with this. My entire site doesn't work without this.

[rpg2009]

Where is the linkbuttonajax function? Difficult to give an answer without seeing it.

The problem is that 'this' isn't in the context of the object firing the event. Instead it's in the context of window.

Try a simple window.getElementById('whatever') and you'll get the same error.

[narutodude000]

I got it working by adding a new parameter to linkbuttonajax(). So now it's like onclick="linkbuttonajax('http://example.com',1,true,this.childNodes[1].childNodes[0]);return false;"

Why does "this" work in the onclick, but not in the function?

[Tcobb]

I'm getting this error: Uncaught TypeError: Object [object DOMWindow] has no method 'getElementsByTagName'

try window.document.getElementsByTagName() instead.

[rpg2009]

Why does "this" work in the onclick, but not in the function?

That's impossible to say without looking at the function. You usually get this issue with events and Internet Explorer as it wrongly binds this to window. There are work arounds for that though.

In your case however I'm guessing it's related to Ajax, which unfortunately I'm not that clued up on.

That said if you are at liberty to post the code for linkbuttonajax, I'm sure someone else here could shed some light on it.

Good you've got it working though.

I got it working by adding a new parameter to linkbuttonajax(). So now it's like onclick="linkbuttonajax('http://example.com',1,true,this.childNodes[1].childNodes[0]);return false;"

That extra parameter sets the context I'm guessing.

Somewhere in there I'm guessing it's using a call or apply, which that parameter is passed into.

Simple example.

var obj = {name:'Fred'};

function sayName(message){ alert (message + this.name) }

// call sayName in the context of obj
sayName.call(obj, 'Hello '); // Hello Fred

[narutodude000]

function linkbuttonajax(url,votes,submitted,button) {
    var xmlHttpReq = false;
    var self = this;
    // Mozilla/Safari
    if (window.XMLHttpRequest) {
        self.xmlHttpReq = new XMLHttpRequest();
    }
    // IE
    else if (window.ActiveXObject) {
        self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
    }
    self.xmlHttpReq.open('POST', '../wp-includes/submit.php', true);
    self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    self.xmlHttpReq.onreadystatechange = function() {
        if (self.xmlHttpReq.readyState == 4) {
            updatelinkbutton(button,self.xmlHttpReq.responseText);
        }
    }
    url=encodeURIComponent(url);
    self.xmlHttpReq.send('v='+votes+'&k=ci3HPCL6gp&url='+url);
if(submitted==false)
window.open('http://linksku.com/submit?url='+url,'submit','width=550,height=550');
}

function updatelinkbutton(num,str){
if((parseFloat(str) == parseInt(str)) && !isNaN(str))
num.innerText = str;
else if(str=='login')
window.open('http://linksku.com/login','login','width=550,height=550');
}

The buttons that call this function is everyone on http://linksku
I want to create a site similar to Digg, where users can "vote" on the best links.