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Browser determination

Posted on 2006-04-17
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Last Modified: 2011-10-03
Many javascript snippets I've seen test to see what kind of browser they are running in using the following methods:

the boolean value of (document.getElementById) is used to indicate whether or not the browser is DOM compatible

the boolean value of (document.all) is used to determine if the browser is IE4

the boolean value of (document.layers) is used to determined if the browser is Netscape 4.

I'd like a brief explanation of why these properties indicate the corresponding browsers.  Thanks.
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Question by:chsalvia
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Roonaan earned 168 total points
ID: 16475549
Because document.layers is not available in IE4 or other browsers and document.all is not available in Netscape.

document.getElementById is currently the most used function to retrieve specific elements in a html tree. In older browsers this function does not exists and therefor needs to be testen on, when you have people with older browser versions in your target public.

-r-
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by:Michel Plungjan
ID: 16475641
However document.all is supposedly available in Opera.
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by:JeffHowden
JeffHowden earned 164 total points
ID: 16475682
You shouldn't be testing for browser.  Instead, you should be testing for object/method support prior to using something that may or may not be supported by the user's browser.
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by:rkattan
rkattan earned 168 total points
ID: 16475997
to detect you could check for
window.opera
which is not supported by any other browser

and to correctly check for IE with document.all you need to do
if (document.all && !window.opera)

like this you exclude opera with document.all
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by:JeffHowden
ID: 16481483
For so many reasons, browser detection is the *wrong* way to go.
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