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What does this mean

P: n/a
I am learning Javascript; and most books only give you partial
definitions for the functions they show you. Here is a line of code
from a browser sniffing function:

var isWin = (navigator.platform.indexOf("Win") !=-1) ? true:false;

What does the -1 stand for.

Excuse me for such a basic question, but I can't find the answer
anyway.

Thanks
Jul 23 '05 #1
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8 Replies


P: n/a
On 17 Sep 2004 09:06:39 -0700, Kim Forbes wrote:
I am learning Javascript; and most books only give you partial
definitions for the functions they show you. Here is a line of code
from a browser sniffing function:
Browser sniffing? If the book burns, it may
be useful to keep you warm for a few minutes,
otherwise it has no (good) use.

Search the group for 'feature detection'. Once
you have the hang of that, you will no longer
need to worry about what browser your visitors
are using.
var isWin = (navigator.platform.indexOf("Win") !=-1) ? true:false;

What does the -1 stand for.


In the string 'AWindowsPC', 'Win' occurs..
^
0123456789
...at index 1.

In the string 'TheWindow', 'Win' occurs
^
0123456789
...at index 3.

...but in the string "ThisIsAnAppleMacintosh",
'Win' occurs ..nowhere. The function returns
-1 to indicate that 'Win' was *not* contained
in the string "ThisIsAnAppleMacintosh".

( ..but use feature detection, browser sniffing
is pointless, stupid, and leads to fragile code. )

HTH

--
Andrew Thompson
http://www.PhySci.org/codes/ Web & IT Help
http://www.PhySci.org/ Open-source software suite
http://www.1point1C.org/ Science & Technology
http://www.lensescapes.com/ Images that escape the mundane
Jul 23 '05 #2

P: n/a
On 17 Sep 2004 09:06:39 -0700, Kim Forbes <ki********@tch.harvard.edu>
wrote:
I am learning Javascript; and most books only give you partial
definitions for the functions they show you. Here is a line of code from
a browser sniffing function:

var isWin = (navigator.platform.indexOf("Win") !=-1) ? true:false;
This could be written as

var isWin = (navigator.platform.indexOf('Win') != -1);

The conditional statement is superfluous as the comparison already
evaluates to a boolean. However, you should avoid this sort of thing (see
below).
What does the -1 stand for.


The String.prototype.indexOf method returns the index of the first
occurance of the supplied string. As in most circumstances, indicies start
at zero (0), so minus one (-1) is used to signify that the substring
couldn't be found.

It's important that you ignore anything regarding browser sniffing. It's a
flawed technique that often results in scripts that break with unknown
user agents, or those that spoof themselves as other browsers. Instead,
you should learn about feature detection. See:

<URL:http://jibbering.com/faq/#FAQ4_26>

and its links.

Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail.
Jul 23 '05 #3

P: n/a
Kim Forbes wrote:
I am learning Javascript; and most books only give you partial
definitions for the functions they show you. Here is a line of code
from a browser sniffing function:

var isWin = (navigator.platform.indexOf("Win") !=-1) ? true:false;

What does the -1 stand for.

Excuse me for such a basic question, but I can't find the answer
anyway.

Thanks


You will only learn if you ask.

isWin is a boolean with values only true or false.

The above is a short way to write an if, else statement.

The -1 means that the String "Win" is not present in the String returned
by navigator.platform If it was the value would have been the first
occurence of the "W" in "Win" starting to count from 0 in the String
returned by navigator.platform. This short statement tests if the user
uses any variant of Windows, in itself a bad thing to do. The
intelligent user uses Linux, or maybe even a Mac.

If you want to I can rewrite that into the mentioned if, else statement
which is more easily understandable.

Chris

Jul 23 '05 #4

P: n/a
Antonie C Malan Snr <ma*******@optusnet.com.au> wrote in message news:<41***********************@news.optusnet.com. au>...
Kim Forbes wrote:
I am learning Javascript; and most books only give you partial
definitions for the functions they show you. Here is a line of code
from a browser sniffing function:

var isWin = (navigator.platform.indexOf("Win") !=-1) ? true:false;

What does the -1 stand for.

Excuse me for such a basic question, but I can't find the answer
anyway.

Thanks


You will only learn if you ask.

isWin is a boolean with values only true or false.

The above is a short way to write an if, else statement.

The -1 means that the String "Win" is not present in the String returned
by navigator.platform If it was the value would have been the first
occurence of the "W" in "Win" starting to count from 0 in the String
returned by navigator.platform. This short statement tests if the user
uses any variant of Windows, in itself a bad thing to do. The
intelligent user uses Linux, or maybe even a Mac.

If you want to I can rewrite that into the mentioned if, else statement
which is more easily understandable.

Chris


Thanks for the answer. Actually, what I would like is a good reference
book where I can learn Javascript inside out. I took a class about a
year ago, but it didn't help me like I wanted. I found many mistakes
in the textbook, and it wasn't as comprehensive as I wanted. What I
want to know is what every line in the code I'm writing means, and why
am I writing that way. As it is now, I can generally write enough code
to get it to do what I want; but I'm not sure why it works like it
does. I'm just parrotting what I learned.
Jul 23 '05 #5

P: n/a
Andrew Thompson <Se********@www.invalid> wrote in message news:<14******************************@40tude.net> ...
On 17 Sep 2004 09:06:39 -0700, Kim Forbes wrote:
I am learning Javascript; and most books only give you partial
definitions for the functions they show you. Here is a line of code
from a browser sniffing function:


Browser sniffing? If the book burns, it may
be useful to keep you warm for a few minutes,
otherwise it has no (good) use.

Search the group for 'feature detection'. Once
you have the hang of that, you will no longer
need to worry about what browser your visitors
are using.
var isWin = (navigator.platform.indexOf("Win") !=-1) ? true:false;

What does the -1 stand for.


In the string 'AWindowsPC', 'Win' occurs..
^
0123456789
..at index 1.

In the string 'TheWindow', 'Win' occurs
^
0123456789
..at index 3.

..but in the string "ThisIsAnAppleMacintosh",
'Win' occurs ..nowhere. The function returns
-1 to indicate that 'Win' was *not* contained
in the string "ThisIsAnAppleMacintosh".

( ..but use feature detection, browser sniffing
is pointless, stupid, and leads to fragile code. )

HTH


Thanks so much. That was exactly what I wanted to know. I started
checking out feature detection, it seems that once I figure it out, it
will be a lot easier to write and implement.

Thanks again.
Jul 23 '05 #6

P: n/a
"Michael Winter" <M.******@blueyonder.co.invalid> wrote in message news:<opsehcj7hnx13kvk@atlantis>...
On 17 Sep 2004 09:06:39 -0700, Kim Forbes <ki********@tch.harvard.edu>
wrote:
I am learning Javascript; and most books only give you partial
definitions for the functions they show you. Here is a line of code from
a browser sniffing function:

var isWin = (navigator.platform.indexOf("Win") !=-1) ? true:false;


This could be written as

var isWin = (navigator.platform.indexOf('Win') != -1);

The conditional statement is superfluous as the comparison already
evaluates to a boolean. However, you should avoid this sort of thing (see
below).
What does the -1 stand for.


The String.prototype.indexOf method returns the index of the first
occurance of the supplied string. As in most circumstances, indicies start
at zero (0), so minus one (-1) is used to signify that the substring
couldn't be found.

It's important that you ignore anything regarding browser sniffing. It's a
flawed technique that often results in scripts that break with unknown
user agents, or those that spoof themselves as other browsers. Instead,
you should learn about feature detection. See:

<URL:http://jibbering.com/faq/#FAQ4_26>

and its links.

Mike


Mike,
I've bookmarked the URL. Thanks.
Jul 23 '05 #7

P: n/a
In article <de**************************@posting.google.com >,
ki********@tch.harvard.edu (Kim Forbes) wrote:
Thanks for the answer. Actually, what I would like is a good reference
book where I can learn Javascript inside out.


This group recommends javascript: The Definitive Guide by David
Flanagan.

Robert
Jul 23 '05 #8

P: n/a
JRS: In article <rc*****************************@news2.west.earthl ink.n
et>, dated Mon, 20 Sep 2004 19:08:11, seen in news:comp.lang.javascript,
Robert <rc*******@my-deja.com> posted :
In article <de**************************@posting.google.com >,
ki********@tch.harvard.edu (Kim Forbes) wrote:
Thanks for the answer. Actually, what I would like is a good reference
book where I can learn Javascript inside out.


This group recommends javascript: The Definitive Guide by David
Flanagan.


AIUI, this group merely considers it to be the best available book.
That is not the same as saying that it will enable one to "learn
Javascript inside out". For that, one should read ECMA-262, and make
all possible deductions from it. One will, also, need to learn about
DOMs.
Learning Javascript inside out can only be possible using multiple
sources of information, and much practice.

--
John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4
<URL:http://www.jibbering.com/faq/> JL/RC: FAQ of news:comp.lang.javascript
<URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources.
<URL:http://www.merlyn.demon.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.
Jul 23 '05 #9

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