可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试):

问题:

IE8 can go into IE7 mode if it needs to. How does jQuery detect this? Specifically, what is the value of $.browser.version?

回答1:

IE8 in IE7 mode will report IE7. BUT you can analyse user-agent and check for "Trident/4.0". If you see this line then you work with IE8

回答2:

The $.browser obejct is populated using a concept know as Browser-Sniffing. Put simply, this is the processes scanning data out of the user-agent string which is sent by browsers, robots, and anything else that accesses the page.

Due to the susceptiblity of the user agent to faking, this object is deprecated in later versions of jQuery. Object Detection and Feature Detection (see $.support) are now used in preference.

For example, Opera 8.5. used to identify itself as IE: http://www.javascriptkit.com/javatutors/navigator.shtml

$.support:

http://docs.jquery.com/Utilities/jQuery.support

User Agents:

http://en.wikipedia.org/wiki/User_agent

http://www.zytrax.com/tech/web/browser_ids.htm

Object detection:

http://www.quirksmode.org/js/support.html http://developer.apple.com/internet/webcontent/objectdetection.html

Browser Sniffing:

http://en.wikipedia.org/wiki/Browser_sniffing

Feature Detection:

http://docs.jquery.com/Utilities/jQuery.support

回答3:

I just tested this out myself (having just downloaded IE8)

When you put IE8 into IE7 compatibility mode with the meta tag like this:

<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />

The value of $.browser.version is still 8.0!

回答4:

JQuery can only see what the browser tells it.

In IE7 mode the browser will report itself as IE7, so that is what JQuery will see.

回答5:

I'm a .NET developer and I always like to use a Sessions.aspx page that I created for this kind'a problems

Fell free to use it, I can share the code as well.

as you can see by this screencast that I just made (14 sec) you get MSIE 8 and MSIE 7 specified in the javascript navigator property, they change when you change compatibility mode as the engine that renders the page is slight different (remember that is not 100% IE7 engine!)

instead of using the jQuery buit in method, just use the normal javascript

IE8 in IE7 mode

4.0 (compatible; MSIE 7.0; Windows NT 6.0; WOW64; Trident/4.0; GTB6; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.30618; .NET CLR 3.5.30729; InfoPath.2; OfficeLiveConnector.1.4; OfficeLivePatch.1.3)

IE8 in native mode

4.0 (compatible; MSIE 8.0; Windows NT 6.0; WOW64; Trident/4.0; GTB6; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.30618; .NET CLR 3.5.30729; InfoPath.2; OfficeLiveConnector.1.4; OfficeLivePatch.1.3)

code:

var browserVersion = navigator.appVersion.toLowerCase();
if(browserVersion.contains('msie 8') ) {
    // IE 8
}
else if(browserVersion.contains('msie 7') ) {
    // IE 7
}