Unexpectedly showing me.. Object is Undefined.

[dmjpro]

Let's see at my code fragment.

var checkBoxes = document.getElementsByTagName("input");
for(var i=0;checkBoxes.length;i++){
 if(checkBoxes[i].type.toLowerCase()=="checkbox" && checkBoxes[i].checked){
 }
}
 

Tell me, how checkBoxes[i] is undefined?
What may be the cause? ;)

[Dormilich]

you've got a syntax error* in line 2.

for(var i=0; checkBoxes.length; i++)

must be

for(var i=0; i < checkBoxes.length; i++)

* technicly it is not an error, but it's not sensible either

[dmjpro]

S**** ... !! Anyway thanks!

[Dormilich]

I've just had such a mistake myself.

[gits]

just a note to speed such nodelist-iterations up ;) ... you could use it the following way:

var nodes = document.getElementsByTagName('input');
 
for (var i = 0, n; n = nodes[i]; ++i) {
    if (n.type.toLowerCase() == 'checkbox' && n.checked) {
        // checked checkbox
    }
}

kind regards

[dmjpro]

How does it speed up? In which sense you are telling? :(

[Dormilich]

and then we're using while-loops, just because we can. *g*

[Dormilich]

@dmjpro
I think because of n = nodes[i] (only one array access)

[gits]

exactly, we don't retrieve the array's length and we just use one array-access per step ... when nodes[i] is undefined the loop terminates ...

kind regards

[dmjpro]

@Dormilich
What do you mean by one array access?

Here two things happen..
First it copies the reference then check whether it is defined or undefined or Null.

But what slows down in my previous one?

[gits]

to use multiple checkBoxes[i] calls is not optimal ...