Browser version detect

以往在處理一些特殊事件時，會針對不同瀏覽器來做不同的fix，jQuery建議不要用瀏覽器來做這種判斷

Rather than using $.browser to detect the current user agent and alter the page presentation based on which browser is running, it is a good practice to perform feature detection. This means that prior to executing code which relies on a browser feature, we test to ensure that the feature works properly. To make this process simpler, jQuery performs many such tests and makes the results available to us as properties of the jQuery.support object.

不過今天遇到一個問題，希望使用者用IE6, IE7, FF3.5以下時要做特殊處理，看起來不難的問題，想說用jQuery.browser來解決即可，沒想到竟然遇到一些問題，例如firefox3.5的版本，$.browser.version竟然不一樣，參考Mozilla_Firefox，如：Firefox3.5對應的version為1.9.1，而這讓我想到一個問題，1.9.1這並不是個數字，因此無法做數字的大小比較。因此我寫了一隻小plugin來處理version版本的比較。

[sourcecode language=”javascript”]
/*

• author: blackbing@gamil.com
• version: 0.1
• date: 2011/01/24
• description: I am confused by browser version detection. What I need is blocking the browsers which are ie6/ie7/ff3 , however, I can’t easily detect browser version. Cause I got the version which is like that "6.0.2900.5512.xpsp_sp3_gdr.100427-1636".
  so I write an easy plugin to check the browser version and you can also use callback to block these kind of old fashion browser or do anything else.

For example:
$.detectBrowserVersion({
filter: {
webkit: ‘535’
},
callback: function(){
alert(‘do you live in stone age?’);
}
});
*/
(function($) {

$.detectBrowserVersion = function(opts) {
    var filter = opts && opts.filter ? opts.filter : {};
    var callback = opts && opts.callback ? opts.callback : null;
    //ready to set stubborn and ignore the setting
    var allcookies = document.cookie;
    var pos = allcookies.indexOf("stubborn=");
    if (pos != -1) {
        var st = pos + 9;
        var end = allcookies.indexOf(";", st);
        if (end == -1) {
            end = allcookies.length;
        }
        var value = allcookies.substring(st, end);
        value = decodeURIComponent(value);
        if (value == '1') {
            return false;
        }
    }
    //these above are ignore the detection
    //filtered browsers and lower version
    var filterBrowsers = {
        'msie': '7',
        'mozilla': '1.9.1'
    };
    filterBrowsers = $.extend(filterBrowsers, filter);
    var default_callback = function() {
        alert('you are using old fashion browser!!');
    };
    callback = callback || default_callback;
    var formatVersion = function(version) {
        //to string
        version += '';
        //get version number
        var versionReg = /[\d]+[\.\d]+/ig;
        var res = versionReg.exec(version);
        if (res && res.length) {
            version = res[0];
        }
        var sp = version.split('.');
        var re = sp[0] + '.';
        for (var i = 1; i < sp.length; i++) {
            re += sp[i];
        }
        return +re;
    };
    $.each($.browser, function(k, w) {
        var filterBrowser = formatVersion(filterBrowsers[k]);
        if ($.browser[k] && filterBrowser) {
            var v = formatVersion($.browser.version);
            if (v <= filterBrowser && callback) {
                //callback and do something
                callback();
            }
        }
    });

};

})(jQuery);
[/sourcecode]

DEMO: http://jsfiddle.net/ynU7Y/

github: https://gist.github.com/793041