如何判断是否为IE浏览器,以及IE浏览器的版本号(IE6,IE7,IE8,IE9)

var isIE = function(ver){
    var b = document.createElement(\'b\')
    if(ver){
    	b.innerHTML = \'<!--[if IE \' + ver + \']>1<![endif]-->\';
    	return b.innerHTML == 1;
    }else{
    	var ver = \'\';
    	b.innerHTML = \'<!--[if IE \' + ver + \']>1<![endif]-->\';
    	return b.innerHTML == 1;
    }
    
}
alert(\'ie6:\' + isIE(6) + \'\n\' + \'ie7:\' + isIE(7) + \'\n\' + \'ie8:\' + isIE(8) + \'\n\' + \'ie9:\' + isIE(9) + \'\n\' + \'ie:\' + isIE());