c o m p . l a n g . j a v a s c r i p t M E T A - F A Q
_________________________________________________________________
T A B L E O F C O N T E N T S
=================================
1 meta-FAQ meta-questions
2 comp.lang.javascript tips
2.1 Which newsgroup deals with javascript?
2.2 What questions are off-topic for clj?
2.3 Why did I get flamed when I posted to clj?
What do I have to do before posting to clj?
2.4 Why was my post not answered?
2.5 How do I direct someone to this FAQ?
2.6 What is ECMAScript? JScript?
2.7 What are object models?
2.8 What is the document object model?
2.9 Internationalisation in javascript.
2.10 I have a question that is not answered in
here or in any of the resources mentioned here
but I'm sure it has been answered in clj. Where
are the clj archives located?
2.11 What does the future hold for ECMAScript?
3 javascript resources
3.1 What books cover javascript?
3.2 What online resources are available?
3.3 Is there a javascript games site?
4 Quick Answers
4.1 How do I protect my javascript code/disable
right mouse button?
4.2 How can I disable the back button in a web browser?
4.3 How can I access the client-side filesystem?
4.4 How can I see in javascript if a web browser
accepts cookies?
4.5 How can I protect a webpage in javascript?
4.6 How do I format 6.57634 to 6.58 or 6.5 to 6.50?
4.7 Why does 5 * 1.015 != 5.075?
4.8 How do I communicate between frames in a web browser?
4.9 How do I find the size of a browser window?
4.10 How do I check to see if a childwindow is open, before opening another?
4.11 Why does framename.print() not print the right frame in IE?
4.12 Why does parseInt(09) give an error?
4.13 How do I get the value of a SELECT box in NN?
4.14 How do I close a window and why does it not work on the first one?
4.15 How do I modify the current page in a browser?
5 Comments
_________________________________________________________________
1.0 meta-FAQ meta-questions
===========================
You are reading the __ comp.lang.javascript __ meta-FAQ, version 6.40
This is the official __ comp.lang.javascript __ (clj) FAQ.
Or, more accurately, the meta-FAQ as it mainly provides URLs
to further information about javascript and some hints and tips
to make your stay in comp.lang.javascript more enjoyable.
This document was created to help reduce the high
levels of noise on clj and to provide a resource for people new
to javascript or who want to know locations of valuable
javascript resources.
The FAQ will currently be posted on Monday, Wednesday and Friday,
until such a time as the regulars feel it can be posted less
frequently.
It is also available on the web at
<URL: http://www.jibbering.com/faq/ >
2.0 comp.lang.javascript tips
=============================
2.1 Which newsgroup deals with javascript?
__ comp.lang.javascript __
is the official Usenet newsgroup dealing with javascript. There
are other newsgroups but many of them are not carried by most
news feeds. clj is an unmoderated newsgroup.
2.2 What questions are off-topic for clj?
clj deals with ECMAScript languages, so any questions about
JavaScript or JScript are welcome - however the group has a
majority of questions about using javascript in a browser,
please make it obvious which host you are using javascript in.
Javascript and Java are two completely different
languages. Java questions should be asked in one of the
comp.lang.java.* newsgroups; they are not appropriate for clj.
Questions dealing with other scripting languages,
such as VBScript, PerlScript or CGI scripting are also off-topic,
as are HTML-only questions.
2.3 Why did I get flamed when I posted to clj?
What do I have to do before posting to clj?
Before posting to clj, you should thoroughly read this
document. You should also thoroughly read the resources mentioned
in section 3. Read FYI28/RFC1855, on Usenet and/or
http://www.jsiinc.com/newsgroup_document.htm
Also you should read all appropriate posts to the clj newsgroup
for several days. Most questions come up at least once every other
day and people can get annoyed of answering them repeatedly.
Please state your question as clearly and concisely as
possible, as this will make it far easier for the other readers
of the list to understand your problems and suggest possible
solutions.
Use the Subject: of your post to indicate the type of problem you
have.
'Help!' or 'I hate Netscape!' are not nearly as useful to
contributors who do not read every post as 'parseInt(09)!=9'.
Has the same question already been posted that day? - if it has
wait to see if the answers to that solve your problem.
Include the script you have been working on (or URL) -
indicate the problem spots and/or previous attempts. Try to limit
the length of your post by removing extraneous page elements, but
avoid removing script unless you are sure it is not an issue, if
the script is long though, please do not post the full script and
just provide a link, as a guide more than 500 lines for a post is
not normally a good idea in any circumstances. A mention of which
platforms and browsers in use or giving problems is also necessary.
Post in plain-text only. Do not post using HTML. If you have
to include your script, paste it in to your post in plain-text,
do not uuencode it or attach it using mime. There is good reason
for this request. Many newsreaders do not read html or mime, and
this limits the number of people who could help you. Before a
reply, quote only the minimum that needs to be quoted.
Don't ask, or at least expect, to be emailed individually.
Some individuals run scams for the purpose of collecting active
email addresses and many won't risk being victimized. If you have
circumstances that won't allow you to read clj for the follow-up,
explain what they are and ask to be CC'ed a copy. You also might
try one of the sites listed in section 3 to read any follow-ups.
Don't take flames too seriously. And don't start a thread
complaining about rude or flippant responses, there is already
enough noise in clj. Keep a sense of humour while posting and
reading and everything will be a lot more enjoyable.
Remember that it is *not* the *job* of posters here to help you.
That the majority of regular posters here do so *voluntarily*
in their free time. They have good days and bad days just like
everyone else.
clj is a technical group, postings of job adverts and commercial
adverts are not welcome - job postings should go to an appropriate
regional jobs group. Annoucements of products of particular revelance
to javascript are welcome, but not more often than once per major
release - then post a short link to your products webpage.
2.4 Why was my post not answered?
This could be for several reasons:
<a>it was a variation of a frequently asked question and was
therefore ignored by everyone
<b>no one knows the answer
<c>the person with the answer has not seen the post
<d>it might not be possible to do what you want to do but
perhaps readers of clj are reluctant to answer your post
in the negative when they are not convinced that it
cannot be done.
2.5 How do I direct someone to this FAQ?
This document is posted to clj very frequently.
There should be no reason to direct someone to it. However, if
someone asks a question answered in this FAQ or in one of the
resources listed herein, please let them know their question is
answered in the FAQ and that the FAQ can be found at
<URL: http://www.jibbering.com/faq/ >
2.6a What is ECMAScript?
<URL: http://www.ecma.ch/ecma1/STAND/ECMA-262.HTM >
ECMAScript is the international standard for javascript.
JScript 3.0 and JavaScript 1.2 (available with version 4.
browsers) are more or less ECMAScript compliant.
Note that ECMAScript did not attempt to standardize the
document object model.
The current edition is Edition 3.0, There is some support
for this edition in JScript 5.0 and JavaScript 1.3,
JScript 5.5 is fully compliant and JavaScript 1.5 available in
released versions of Netscape 6 is compliant but for a few missing
methods. (JS1.5 available in later Mozilla builds is fully
compliant)
2.6b What is JScript?
JScript is Microsoft's implementation of ECMAScript.
2.7 What are object models?
Object models (OMs) are not part of the javascript language,
they are provided by the host to allow javascript (or other
scripting language) to communicate with the host. An object
model may allow a javascript to access a file system, or
control a nuclear power station. The most commonly used
object models via javascript are provided by Active Server
Pages, Server Side JavaScript, and the Windows Script Host.
The most common of all of course is the Document Object
Model (DOM) provided by web browsers.
2.8 What is the Document Object Model?
This is the collection of objects provided by each browser.
Basically, any object in the window hierarchy is part of the DOM.
This means that document.writeln(), for example, is not a
javascript method but is, in fact, a method provided by the DOM.
The DOM has been standardised by the w3 consortium however like all
w3 standards browser support unfortunately is not there yet. Most
cross-browser coding problems come from slightly different
implementations of the DOM in the different browsers.
<URL: http://www.w3.org/TR/REC-DOM-Level-1/ >
Level 2 of the DOM standard is already in draft.
2.9 Internationalisation in javascript.
There is little Internationalisation capability in javascript,
the various toString() methods are all implementation dependant,
but tend to use UK/US settings. ECMAScript Edition 3.0 has introduced
some capability including the toLocaleString() method which should
create a string based on the hosts locale. In future versions
of javascript it is expected that there will be much more support.
2.10 I have a question that is not answered in here
... or in any of the resources mentioned here but I'm sure it
has been answered in clj. Where are the clj archives located?
<URL: http://groups.google.com/ >
Maintain a usenet archive going back many years, although
currently only 6 months are available to search.
2.11 What does the future hold for ECMAScript?
The ECMAScript Technical commitee is now working on Edition 4, the
first implementation of which is likely to be JScript.NET, which has
been made available in a preview release, and should beta before too
long, which includes a compiler, allowing you to create standalone
JScript executables.
Edition 4.0 of ECMAScript provides new features like typed variables,
classes, other information can be found at:
<URL: http://msdn.microsoft.com/voices/scripting07142000.asp >
or from the newsgroup microsoft.public.net.jscript.general
3.0 Javascript resources
========================
3.1 What books cover javascript?
There are rather a lot of javascript books
available, and if anyone has an example of an up to date
good javascript book, I'll gladly add it to the faq.
3.2 What online resources are available?
Javascript FAQ sites, please check these first:
<URL: http://www.irt.org/script/faq.htm >
<URL: http://javascript.faqts.com/ >
Index of docs online and for download:
<URL: http://docs.iplanet.com/docs/manuals/javascript.html >
(D)HTML reference:
<URL: http://msdn.microsoft.com/workshop/author/dhtml/reference/dhtmlrefs.asp >
JScript reference and main Microsoft script site:
<URL http://msdn.microsoft.com/scripting/jscript/doc/jstoc.htm >
<URL: http://msdn.microsoft.com/scripting/ >
Archived documentation for MSIE 3.x:
<URL: http://members.tripod.com/~housten/download/ >
The official ECMAScript specification:
<URL: http://www.ecma.ch/ecma1/STAND/ECMA-262.HTM >
DOM level 1 ECMA script binding:
<URL: http://www.w3.org/TR/REC-DOM-Level-1/ecma-script-language-binding.html >
FESI - a free implementation of ECMAScript in Java:
<URL: http://home.worldcom.ch/~jmlugrin/fesi/index.html >
Frequently asked questions about source code obfuscation:
<URL: http://ugweb.cs.ualberta.ca/~thompson/programming/javascript/protect.html >
Sites discussing Active Server Pages:
<URL: http://www.15seconds.com/ >
<URL: http://www.4guysfromrolla.com/ >
<URL: http://www.aspfaq.com/ >
DHTML source code and tutorials to a high standard:
<URL: http://www.dansteinman.com/dynduo/ >
<URL: http://www.w3schools.com/ >
Sites focused on using Scripting to automate Windows:
<URL: http://www.windows-script.com/ >
<URL: http://cwashington.netreach.net/ >
Code for manipulating dates in javascript:
<URL: http://www.merlyn.demon.co.uk/js-dates.htm >
Games written in javascript:
<URL: http://www.javascript-games.org/ >
4.0 Quick Answers
==================
4.1 How do I protect my javascript code/disable right mouse button?
In the main you don't, as the language is interpreted, you need
to deliver the source code, with JScript, there is the Script
Encoder (see MSDN) but this is nothing more than obfuscation
in effect, disabling the Right Mouse button, also achieves
nothing to protect your script in a web browser.
Your code is likely protected under copyright laws see:
< URL: http://www.wipo.org/eng/general/copyrght/intro.htm >
< URL: http://html.about.com/compute/html/msubcopyright.htm >
4.2 How can I disable the back button in a web browser?
You can't, the browsers history cannot be modified, you can however
use location.replace(url) in some browsers to replace the current
page in the history.
4.3 How can I access the client-side filesystem?
Security means that by default you can't, in a more restricted
enviroment, there are options, (e.g. live connect to Java in NN,
and using FileSystemObject in IE) check http://groups.google.com/
for previous posts on the subject.
4.4 How can I see in javascript if a web browser accepts cookies?
Writing a cookie, reading it back and checking if it's the same.
4.5 How can I protect a webpage in javascript?
You can't security needs to be done serverside, client side
protection does not work.
4.6 How do I format 6.57634 to 6.58 or 6.5 to 6.50?
In ECMAScript Ed. 3.0 (JScript 5.5 (but buggy)/JavaScript 1.5)
num.toFixed(2)
or for previous versions:
Math.round(num*100)/100, (doesn't add trailing zeros.)
Adding trailing zeros is more complicated to achieve without
failing for some numbers, the below from
< http://www.merlyn.demon.co.uk/js-maths.htm#Round > work
successfully (slightly modified to add the prototype to the
number object.)
function Stretch(Q, L, c) { var S = Q
if (c.length>0) while (S.length=0.0
var T, S=new String(Math.round(X*Number("1e"+N)))
if (S.search(/e/)!=-1) { return ''+X }
with (new String(Stretch(S, M+N, '0')))
return substring(0, T=(length-N)) + '.' + substring(T) }
function Sign(X) { return X<0 ? '-' : ''; }
function StrS(X, M, N) { return Sign(X)+StrU(Math.abs(X), M, N) }
Number.prototype.toFixed= new Function('n','return StrS(this,1,n)')
4.7 Why does 5 * 1.015 != 5.075?
Numbers which are finite in Decimal, maybe recurring in
the Binary system used inside javascript, see 4.6 on how
to cope with this feature.
4.8 How do I communicate between frames in a web browser?
To reference another frame, you simply need to step through the
frame hierachy, parent is the page the frame is defined in,
parent.framename is another frame in the same frameset as the
frame you are in. So to access a variable called Moomin in a
frame called Snork that is in the same frameset you're in you
would use parent.Snork.Moomin, to call the function Snufkin
in that frame you would use parent.Snork.Snufkin() .
4.9 How do I find the size of a browser window?
Where supported in NN: (>NN4.0)
var winWidth = window.innerWidth;
var winHeight = window.innerHeight;
Where supported in IE: (>IE4.0)
var winWidth = document.body.clientWidth;
var winHeight = document.body.clientHeight;
4.10 How do I check to see if a child window is open, before
opening another?
var myWin=null;
function openWin(aURL) {
if (!myWin || myWin.closed ) {
myWin=window.open(aURL,'myWin');
} else{
myWin.location=aURL;
myWin.focus();
}
}
4.11 Why does framename.print() not print the right frame in IE?
IE prints the frame that has focus when you call the print method:
frameref.focus();frameref.print();
4.12 Why does parseInt(09) give an error?
parseInt decides what base the number is by looking at the
number, by convention it assumes any number beginning with 0 is
Octal, and any number beginning with 0x Hexadecimal, to force
use of base 10 add a second parameter parseInt(09,10)
4.13 How do I get the value of a SELECT box in NN?
el=document.forms['formname'].elements['elementname'];
value=el[el.selectedIndex].value;
4.14 How do I close a window and why does it not work on
the first one?
windowref.close(); windowref is window, or self, top, parent, or a
reference obtained when opening the window, you can only close
windows opened by script, no others.
4.15 How do I modify the current page in a browser?
At its simplest in current DOM2 (with innerHTML extension)
(IE5+ NS6 ) then:
HTML: < div id="aID">Some Content</div>
Script:
document.getElementById("aID").innerHTML="Some <em>new</em> Content";
works, it is possible though in IE 4+, NS 4+, code
like below achieves it, but not without many problems in more
complicated situations than described, be careful:
HTML:<div ID=aID><ilayer name=aID>Some Content</ilayer></div>
Script:
DynWrite('aID',"Some <em>new</em> Content")
With the below code also in the page:
DocDom = (document.getElementById?true:false);
DocLay = (document.layers?true:false);
DocAll = (document.all?true:false);
DocStr=''
if (DocLay) DocStr="return document.layers[id]"
if (DocAll) DocStr="return document.all[id]"
if (DocDom) DocStr="return document.getElementById(id)"
GetRef=new Function("id", DocStr)
if (DocStr=='') { DynWrite=new Function("return false") } else {
if (DocAll || DocDom) {
DynWrite=new Function("id", "S", "GetRef(id).innerHTML=S; return true")
}
if (DocLay) DynWrite=new Function("id", "S", "var x=GetRef(id).document;"+
"x.open('text/html'); x.write(S); x.close(); return true")
}
5.0 Comments
=============
There have been many contributors to this FAQ in its history,
thanks to them all for a list see:
<URL: http://www.jibbering.com/faq/contributors.html >
If you have any suggestions for the FAQ, or further questions
that you feel should be answered here, please e-mail me at the
address below.
=========================
FAQ Maintained by Jim Ley - Jim@Jibbering.com