SRC= and missing .JS file

Paul Gorodyansky · Apr 9, 2004

Hi,

Could not find the answer neither in FAQs not on the Web...

On many javaScript 'tips' sites they say that do warn the user
regarding missing .JS file one should do the following:
<html>
<head>
....
<script src="ABC.js" ...>
alert("Error! Included JS file not found ...");
</script>
</head>
....

But it does NOT work neither in my IE 6 nor in my Mozilla 1.6 -
no alert when the .JS file does not exist.

http://www.htmlhelp.com/reference/html40/special/script.html

says,
"When the SRC attribute is used, the embedded script is ignored."
which does not touch the case when .JS not found
(or does it? Ignored _always_?)

So how to tell the user that .JS to be included was not found?

--
Regards,
Paul
http://KBD.da.ru - was possible to develop only because
of the great article at
http://www.faqts.com/knowledge_base/view.phtml/aid/1661

Paul Gorodyansky · Apr 10, 2004

Hi,

I've been experimenting with the following and it seems to work. In the
.js file put the following statement at the top.
var script111loaded = "true";

Now in the HTML put
<script type="text/javascript">
if (!script111loaded) {alert("script 111 not loaded")};
</script>

Thanks, it works (though, I had to declare that variable
at the top of my _html_ text,too - otherwise _if_ did not
work - just has "undefined" error in JS Console, at least
in Mozilla 1.6).

Dr John Stockton · Apr 10, 2004

JRS: In article <[email protected]>, seen

Could not find the answer neither in FAQs not on the Web...

So how to tell the user that .JS to be included was not found?

I test for the existence of a variable declared in it.

I don't know about putting material here --------+
V
<script type="text/javascript" src="include1.js"> </script>

Dr John Stockton · Apr 10, 2004

JRS: In article <090420041736545389%[email protected]>, seen in

news:comp.lang.javascript said:
I've been experimenting with the following and it seems to work. In the
.js file put the following statement at the top.
var script111loaded = "true";

Now in the HTML put
<script type="text/javascript">
if (!script111loaded) {alert("script 111 not loaded")};
</script>

Why did you choose to assign a string to script111loaded ?
<rhetorical> How about "false", "banana", or just 1 ?

Yann-Erwan Perio · Apr 11, 2004

if(!this.script111loaded) //...

Why did you choose to assign a string to script111loaded ?
<rhetorical> How about "false", "banana", or just 1 ?

Well, any non-empty string would technically type-convert to true,
though I question the semantic value of "banana" for maintenance
purposes...

As you suggest, using a boolean instead of a string would definitely be
a good idea!

Richard Cornford · Apr 11, 2004

I can understand why a script may care that a file on which it is
dependent has not loaded, but I don't see much point in telling the user
in most cases as there is not going to be a great deal that they can do
about it (assuming that they understand the role of a JS file in the
first place).

I test for the existence of a variable declared in it.

I don't know about putting material here --------+
V
<script type="text/javascript" src="include1.js"> </script>

One of the problems with this is how the server reacts to its inability
to find the file. A suitable HTTP error response should tell the browser
that something is up, but many servers are configured to send custom
HTML pages that announce the error to the user but might still give the
browser the impression that the resource that was requested has been
returned. And an HTML file sent in the pace of a JS file will produce a
syntax error, but not necessarily result in the fall-back to using the
contents of the script element.

Richard.

Paul Gorodyansky · Apr 11, 2004

Hello!

Richard said:
One of the problems with this is how the server reacts to its inability
to find the file. A suitable HTTP error response should tell the browser
that something is up, but many servers are configured to send custom
HTML pages that announce the error to the user but might still give the
browser the impression that the resource that was requested has been
returned. And an HTML file sent in the pace of a JS file will produce a
syntax error, but not necessarily result in the fall-back to using the
contents of the script element.

Richard.

it was exactly my reason to post the question here - with
my ISP - CompuServe - *nothing* happens - page loads,... -
no error of any kind, so a user is just
confused why the expected functionality failing - _I_
need to explain the user why

BTW, obviously I used a _Boolean_ variable after getting
a response here

Michael Winter · Apr 15, 2004

On Sat, 10 Apr 2004 08:10:47 -0700, Dennis M. Marks

[snip]

Why doesn't a test like "if (document.getElementById) {xxx}" give an
undefined error in some browsers, or does it?

In Opera, Mozilla and IE, it does. It probably does in every browser.

If the OP wants to avoid getting "undefined" errors, you could do

if( 'undefined' == typeof scriptXXXloaded ) {
// script XXX is not loaded
}

and declare scriptXXXloaded somewhere in the script

var scriptXXXloaded = true;

This will avoid the need to declare the variable in the containing HTML
file. The value of the variable itself is irrelevant, just so long as it's
not undefined.

Mike

Richard Cornford · Apr 15, 2004

Michael said:
On Sat, 10 Apr 2004 08:10:47 -0700, Dennis M. Marks

[snip]

Why doesn't a test like "if (document.getElementById) {xxx}" give an
undefined error in some browsers, or does it?

Click to expand...

In Opera, Mozilla and IE, it does. It probably does in every browser.

<snip>

"if (document.getElementById) {xxx}" - will only produce an undefined
error if - document - is undefined (and a different error if null).
Reading a non-existent property form an object returns an undefined
value, which happily type-converts to boolean false for the expression
of the - if - statement (no errors result).

The OP's problem with - if(!script111loaded) { ... }; - is that the
scope chain resolution of the identifier for an undeclared (and
unassigned) global variable has a null base object on the returned
Reference, and the subsequent use of that Reference with the internal -
GetValue - function is required to throw an exception when the base
object is null.

The typeof operator avoids the problem as it has special handling when a
Reference has a null base object, but a property accessor, where the
identifiers before the property name refer to existing objects, will
never return a Reference with a null base object (so it will never throw
an exception when used with - GetValue).

Richard.

Michael Winter · Apr 16, 2004

Michael said:
Michael said:

On Sat, 10 Apr 2004 08:10:47 -0700, Dennis M. Marks

[snip]

Why doesn't a test like "if (document.getElementById) {xxx}" give an
undefined error in some browsers, or does it?

Click to expand...

In Opera, Mozilla and IE, it does. It probably does in every browser.

Click to expand...

"if (document.getElementById) {xxx}" - will only produce an undefined
error if - document - is undefined (and a different error if null).
Reading a non-existent property form an object returns an undefined
value, which happily type-converts to boolean false for the expression
of the - if - statement (no errors result).

[snip]

The problem isn't with the conditional expression, it is with xxx itself.
I would guess that as xxx hasn't been previously defined, and isn't part
of an assignment (where the variable would become global), the interpreter
is trying to evaluate something that obviously doesn't exist, hence the
undefined error.

Mike

Richard Cornford · Apr 16, 2004

The problem isn't with the conditional expression, it is with xxx
itself. I would guess that as xxx hasn't been previously defined, and
isn't part of an assignment (where the variable would become global),
the interpreter is trying to evaluate something that obviously
doesn't exist, hence the undefined error.

Ah, you are being unusually pedantic. I took the - xxx - as standing in
for some unspecified block of code to be executed if -
document.getElementById - type-converted to true. I usually use - ... -
in that context, which will also predictably error if actually executed.

Richard.

Using JS to verify registration info?	1	Mar 19, 2020
Missing JS file errors with MSIE . Help !!	19	Sep 25, 2006
Quicktime and JS - what am I missing?	1	Jun 20, 2007
Changing IFrame Src Leak in Internet Explorer	1	Dec 9, 2008
Include .js file inside HTML and call functions from another <script>	11	Apr 5, 2006
How to save JSON Data to a file using fetch() api?	2	Apr 28, 2022
js importing problem	34	Apr 15, 2009
What is the error in this code , file not fetch and not fetched in the basemap, not vissible in the browser	1	Jul 26, 2023

SRC= and missing .JS file

Paul Gorodyansky

Paul Gorodyansky

Dr John Stockton

Dr John Stockton

Yann-Erwan Perio

Richard Cornford

Paul Gorodyansky

Michael Winter

Richard Cornford

Michael Winter

Richard Cornford

Ask a Question

Similar Threads

Members online

Forum statistics

Latest Threads