Simplest getElementById question ever.

Rich Hephner

Why isn't this working?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<script language="javas cript">
alert(document. getElementById( 'pst'));
</script>
</head>

<body>
<div id="subjects">
<form action="" method="get">1. Would you like to
<div id="pst">
<a href="#">write a supporting opinion</a>, or <a href="#">write a
differing opinion</a>, or <a href="#">write a general comment</a>
</div>
<p id="subject_lis t"> </p>
</form>
</div>
</body>
</html>

It's killing me. Is there something obvious I'm missing? Thanks.

Jul 23 '05 #1

Subscribe Reply

1423

KEN TIBBETTS

The document has to load before you can reference document.getEle mentById;

wrap it in a function and call it onload:

<script language="javas cript">
function saywhat(){
alert(document. getElementById( 'pst'));
}
onload=sayWhat;
</script>

Jul 23 '05 #2

Martin Honnen

Rich Hephner wrote:

Why isn't this working?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<script language="javas cript">
alert(document. getElementById( 'pst'));
</script>

The browser parses the document and executes script blocks while parsing
it so at this point when document.getEle mentById('pst') is called it
returns null as no element with that id attribute value is found. So the
example works as expected if you see an alert dialog with null.
Perhaps you want to use
window.onload = function (evt) {
alert(document. getElementById( 'pst'));
};

--

Martin Honnen
http://JavaScript.FAQTs.com/

Jul 23 '05 #3

Evertjan.

Rich Hephner wrote on 16 mei 2005 in comp.lang.javas cript:

Why isn't this working?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<script language="javas cript">
alert(document. getElementById( 'pst'));
</script>
</head>

<body>
<div id="subjects">
<form action="" method="get">1. Would you like to
<div id="pst">
<a href="#">write a supporting opinion</a>, or <a href="#">write a
differing opinion</a>, or <a href="#">write a general comment</a>
</div>
<p id="subject_lis t"> </p>
</form>
</div>
</body>
</html>

It's killing me. Is there something obvious I'm missing? Thanks.

1 the element does not yet exist at the time your alert is executed.

2 you probably don't want to show the element, but some writable property
of that element, like the tagNeme, some style element or the innerHTML.
IE would return [object] but other browsers could have other ideas.

--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

Jul 23 '05 #4

Rich Hephner

Wow. Thanks. That's it. One more question though. How come if I create
an external js file like so:

function test(){
alert(document. getElementById( 'pst'));
}

if(document.get ElementById && document.create TextNode){
window.onload = test();
}

and call it from the head of the first html file, it doesn't work?
Thanks.

Jul 23 '05 #5

Evertjan.

Rich Hephner wrote on 16 mei 2005 in comp.lang.javas cript:

Wow. Thanks. That's it.
It would be even better if you qoute the stuff you are replying on.

This is not email, nor a helpdesk service, but usenet, and thousands of
readers now and later the archive, don't know a thing of where you are
relying on.

One more question though. How come if I create an external js file like so:

function test(){
alert(document. getElementById( 'pst'));
}

if(document.get ElementById && document.create TextNode){
window.onload = test();
}

and call it from the head of the first html file, it doesn't work?
Thanks.

The same answer would apply if the first was still in your quote.

Please keep to the Netiqutte.
--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

Jul 23 '05 #6

Martin Honnen

Rich Hephner wrote:

How come if I create
an external js file like so:

function test(){
alert(document. getElementById( 'pst'));
}

if(document.get ElementById && document.create TextNode){
window.onload = test();
}

and call it from the head of the first html file, it doesn't work?

Well it works, you declare a function named test and then you call it on
the right hand of the expression
window.onload = test();
then the function is called and executes
document.getEle mentById('pst')
which at that time does not find an element with that id and returns
null which is displayed.

What you probably want is
window.onload = test;
or
window.onload = function (evt) {
test();
}
--

Martin Honnen
http://JavaScript.FAQTs.com/

Jul 23 '05 #7

Rich Hephner

--- quote --

Rich Hephner wrote:

How come if I create
an external js file like so: function test(){
alert(document. getElementById( *'pst'));
}
if(document.get ElementById && document.create TextNode){
window.onload = test();
}
and call it from the head of the first html file, it doesn't work?

Well it works, you declare a function named test and then you call it
on
the right hand of the expression
window.onload = test();
then the function is called and executes
document.getEle mentById('pst')
which at that time does not find an element with that id and returns
null which is displayed.

What you probably want is
window.onload = test;
or
window.onload = function (evt) {
test();
}
-- end quote --

Thank you Martin. That's what I needed to here. I'm a long time
javascript programmer, but am just now starting to take full advantage
of the new DOM. Thanks for your patience and your help.

Jul 23 '05 #8

Rich Hephner

>Rich Hephner wrote on 16 mei 2005 in comp.lang.javas cript:

Wow. Thanks. That's it.

It would be even better if you qoute the stuff you are replying on. This is not email, nor a helpdesk service, but usenet, and thousands ofreaders now and later the archive, don't know a thing of where you are relying on.

One more question though. How come if I create
an external js file like so: function test(){
alert(document. getElementById( *'pst'));
}
if(document.get ElementById && document.create TextNode){
window.onload = test();
}
and call it from the head of the first html file, it doesn't work?
Thanks.

The same answer would apply if the first was still in your quote. Please keep to the Netiqutte.
--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

Thanks for the scolding. I'm using Google groups for posting because
that's all I have access to at my current location. They don't make it
easy to quote from past postings. I'm well aware of the Netiquette.

Jul 23 '05 #9

Evertjan.

Rich Hephner wrote on 16 mei 2005 in comp.lang.javas cript:

Thanks for the scolding. I'm using Google groups for posting because
that's all I have access to at my current location. They don't make it
easy to quote from past postings. I'm well aware of the Netiquette.

Is that a compelling argument not to do your utmost?

I am told it is quite possible.

--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

Jul 23 '05 #10

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