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Detecting Opera

The simplest and best way to begin browser detection is to start with the

problem

browsers, such as

Opera and Safari. If you determine that a browser is not one of these, it is much easier to determine

when a browser is legitimately IE or Mozilla.

To begin, consider the possible Opera user-agent strings:

Opera/7.54 (Windows NT 5.1; U)

Mozilla/5.0 (Windows NT 5.1; U) Opera 7.54

Mozilla/4.78 (Windows NT 5.1; U) Opera 7.54

Mozilla/3.0 (Windows NT 5.1; U) Opera 7.54

Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) Opera 7.54

One thing that jumps out right away is that each of these strings has the word

“Opera”

. So the easiest

way to determine if the browser is Opera is just to search for that string:

var isOpera = sUserAgent.indexOf(“Opera”) > -1;

When you know you have an Opera browser, you can go ahead and determine the actual version. The

first step is to define several variables to test for the various versions of Opera.

To determine what version of Opera is being used, you can define some variables:

var isMinOpera4 = isMinOpera5 = isMinOpera6 = isMinOpera7 = isMinOpera7_5 = false;

This code uses compound assignment to set each variable to an initial value of

false

, ensuring that if

the browser is Netscape, these variables return the correct value.

Naturally, you shouldn’t even bother setting these variables unless the browser has been identified as

Opera, so any further evaluation of the browser version needs to take place inside of an

statement:

if (isOpera) {

//version detection here

}

Because of Opera’s disguises, you have two different ways to determine the browser version. If Opera is

using its own user-agent string, the version is contained in

fAppVersion

, which was defined earlier.

You can check to see if Opera is using a disguise by checking

navigator.appName

; if it equals

“Opera”

then the browser isn’t using a disguise.

You could also use a regular expression to do this check; however, regular expres-

sions aren’t supported by some earlier browsers and could cause an error when the

line is executing. Using

indexOf()

ensures that this line works because the method

has been included since the very first version of JavaScript.

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Browser and Operating System Detection

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