What is the correct way to detect Opera using jQuery?

问题

Amazon.com recently updated their javascript, and it's causing problems with some Opera browsers.

Their browser detection code looks like so, but it's faulty:

    function sitbReaderIsCompatibleBrowser() {
        if (typeof(jQuery) == 'undefined') {
            return false;
        } else {
            var version = jQuery.browser.version || "0";
            var splitVersion = version.split('.');
            return (
                   (jQuery.browser.msie && splitVersion[0] >= 6)  // IE 6 and higher
                || (jQuery.browser.mozilla && (
                       (splitVersion[0] == 1 && splitVersion[1] >= 8) // Firefox 2 and higher
                    || (splitVersion[0] >= 2)
                   ))
                || (jQuery.browser.safari && splitVersion[0] >= 500) // Safari 5 and higher
                || (jQuery.browser.opera && splitVersion[0] >= 9) // Opera 5 and higher
            );
        }
}

Nothing obviously wrong jumps out at me with this code, but I've never used jQuery before so I don't know.

Even though this code looks like it's attempting to let Opera users through, when I visit the page with Opera 9.64 I get an "unsupported browser" message. If I change Opera's settings to report itself as Firefox, the page works perfectly! With that in mind, I'm pretty sure it's a problem with the script and not the browser.

Any jQuery experts have a suggestion?

You can replicate the behavior by visiting any book on Amazon and clicking the "look inside this book" link.

回答1:

Prior to jQuery 1.3, you could use jQuery.browser:

if( $.browser.opera ){
  alert( "You're using Opera version "+$.browser.version+"!" );
}

From version 1.3, you should use jQuery.support instead.

Main reason for this is that should should avoid checking for browsers, as features may change from version to version, making your code obsolete in no time.

You should always try to use feature detection instead. This will allow you to see if current browser supports the feature you're trying to use, regardless the browser brand, version, etc.

回答2:

There is a special window.opera object which is present in all Opera 5+ browsers. So something as simple as:

if (window.opera && window.opera.buildNumber) { 
    // we are in Opera 
}

would be enough.

回答3:

I check for Opera like this:

if (/Opera/.test (navigator.userAgent)) // do something

Why would you want jQuery?

回答4:

It is much better to detect javascript capabilities rather than browser userAgent.

ie DOM, XmlHttpRequest, eventing model (event.target vs event.srcElement), ActiveX, Java etc

By focusing on the API functions that you will require, rather than a target browser you will create a more robust set of scripts, and inevitably less special casing.

This link here at opera will probably tell you more

回答5:

A very simple way from Opera themselves:

if (window.opera) {
    //this browser is Opera
}

Source: http://my.opera.com/community/openweb/idopera/

回答6:

The main reason why Amazon fails on Opera is because the send different code from the server side already... If you visit the same page with Firefox and then save that page and reopen it in Opera it works fine...

But they promised to fix that sometime in January...

回答7:

I don't know for sure ( i never really check for opera anyway) but if the built-in jQuery functionality doesn't detect opera, may be a bug with the jQuery which needs to be fixed. I would suspect if that's the case, it should get resolved fairly quickly.

回答8:

In current HTML5 times, you can also check for browser features instead often.

if (!window.FormData) { alert("xmlhttprequest L2 FormData interface not available"); }

回答9:

I think this way is the best
if ( window.opera.version() == 12) { }
This example check if opera version is 12. Very useful when I have problems with font-face in Opera.

来源：https://stackoverflow.com/questions/644903/what-is-the-correct-way-to-detect-opera-using-jquery