Document nodes returning null

[drdeath89]

Im writing some Javascript code that requires me to loop all child nodes and sub child nodes of a certain parent node and execute a function with the child node in question.

I decided to write a recursive function with said functionality, with a node and a function as parameters, but it simply wont work.

My problem is that whenever i pass a node to this function parameter it is always, regardless of what i change, equal to null. I even modified my custom passed function to ignore null nodes, and now it throw a null variable error every time my function recurses.
(exact error: node.childNodes has no properties)

To me it looks like a problem with these infamous 'closures' i keep hearing about. I understand the concept, but I dont know exactly how they work in this context due to a great lack of experience :(.

I know there are many sample codes out there that can do the job, but I want to know why THIS function, which looks perfectly logical to me, doesnt behave as i would expect it too.

I read a few posts here and there relating to this, and I modified my code accordingly, but i cant seem to figure out just what is causing my problem.

var ProcNodes=function(node,fn)
{
    var n=0,
        i=0,
        nodes=node.childNodes,
        length=nodes.length;
    for(i=0;i<length;i++)
    {
        var node=nodes[i];
        fn.call(node);
        if(node.childNodes.length>0)
            n+=ProcNodes(fn,node);
        n++;
    }
    return n;
}

thx in advance,
Yoann Arseneau

[gits]

hi ...

welcome to TSDN ...

i fixed your code ... have a close look at the example ... i tested it with google.com in firebug and it worked:

var ProcNodes = function(node, fn) {
    var nodes  = node.childNodes;
    var length = nodes.length;
 
    for (var i = 0 ; i < length; i++) {
        var node = nodes[i];
 
        fn.call(node);
 
        if (node.childNodes.length > 0) {
            ProcNodes(node, fn);
        }
     }   
}
 
ProcNodes(document.getElementsByTagName('body')[0], function() {
    alert(this.nodeType);
});
 

we don't need the n and i fixed the order of params in the recursion call

kind regards

[drdeath89]

heh... well im kinda embarrassed :\

thx for your help XD

[mrhoo]

Excuse this- I missed gits post.

nodecall= function(node,fun){
    var n= [],tem;    
    tem= node.firstChild;
    while(tem){        
        n.push(fun.call(tem));
        if(tem.hasChildNodes()) n.push(arguments.callee(tem,fun));
        tem= tem.nextSibling;        
    }
    return n;
}

function ahoy(){
    return this.nodeName;
}

var A=nodecall(docu ment.body,ahoy) ;
alert(A.join('\ n\n'));

[gits]

heh... well im kinda embarrassed :\

thx for your help XD

hi ...

no problem ... post back to the forum anytime you have more questions ...

kind regards

[drdeath89]

Im still getting some null nodes, but i think i just figured it out.

From what i can tell, firefox (browser im currently testing on) returns whitespace textnodes as null objects.

Can someone confirm this so i can finally stop worrying about this insignificant part of my app :\

[gits]

it returns them as textnodes ... nodeType == 3 or nodeName == '#text' ... so with that you may handle them ... could tell where you get a null-value?

[drdeath89]

if(node==null)
{
    alert("ParseNode: null node");
    return;
}

this message alerts several times during my loop, it is the first statement inside my calling function (fn parameter)

<EDIT>
the node variable is the one directly passed from the recursive function

[gits]

hmmm ... that is strange ... could you post your html ... i think in case of a text node it should alert a '[object Text]' ...

[drdeath89]

Well this is prety wierd... When i changed the statement on line 7 my script suddenly started acting exactly like expected.

var ProcNodes=function(node,fn)
{
    var nodes=node.childNodes,length=nodes.length,n=0;
    for(var i=0;i<length;i++)
    {
        var node=nodes[i];
        if(!fn(node))// was previously fn.call(node)
            return-n;
        if(node.childNodes.length>0)
            n+=ProcNodes(node,fn);
        n++;
    }
    return n;
}

(the n variable is there because i need it for debugging purposes)

Honestly, I only used the call method because I saw another script use it and I thought it looked cool. :P
I assumed it worked identical to normal calling syntax which appears not to be the case, atleast not on my firefox. Can anyone confirm if there is a difference between these two lines of code?

someFunction("parameter")
someFunction.call("parameter")

<Edit>And yes, it does alert text node objects for whitespace nodes with the new code