Explanation of the world's shortest IE decision if (!+[1,])

<script type= "Text/javascript" >alert ([+]);//equivalent to alert ([1,2].tostring ());  --This is the same on IE and non-ie, will pop up " "Alert" ([1,]);//equivalent to alert ([1,].tostring ()),--in non-IE standard browser, JS engine will automatically delete the last ",", so on IE will pop up "1," and on non-ie will pop up "1" alert (+[1, ]);//According to the above explanation, this sentence on IE equivalent to alert (+ "1,"), and on non-ie equivalent to alert (+ "1"), the role of positive sign is to try to convert the string to a number, "1," of course, is not a number, and "1" can be converted to the number 1 So the final result: IE will fail to pop "NaN", instead of the number "1" on IE will pop up the  //above the + number conversion string for the number of the test var s = + "5"; alert (s+1);  / /ok, so far, we know  +[1,]  finally in IE for the NaN, in the non-IE browser is the digital 1 //below to see the very personality of Nanalert (nan==true);//Popup   Falsealert (Nan==false);//pop-up  falsealert (Nan==nan);//pop-up  false //that is NaN no matter who compares with Falsealert (! NaN);//equivalent to alert (! ( Nan==true)), according to the above explanation of course is pop true  //so, alert (!+[1,])   Finally on IE will pop up "true", and then look at Firefox and other non-IE browser performance alert ( New boolean (0));//falsealert (New boolean (1));//truealert (New boolean ( -1));//true// That is: The number 0 will be converted to false, any other number will be converted to true, so ultimately on non-IE browser is ultimately equivalent to: alert (!1),//That is, alert (!true)//will eventually get false // In summary: The following judgment will be able to determine whether the browser is ieif  (!+[1,]) {     alert ("I am a real IE browser!")} Else{    alert ("I'm Not ie!")} </script>

Note: Over time, IE9 and above have fixed the bug (unless it is set to compatibility mode), which has already been pointed out in the original reply of the Szeto. There are many ways to detect IE, it is not necessary to use this kind of kinky technique, the original reply, and the other method of Stu

if (!window.            VBArray) {alert ("not IE");            } else{alert ("IE"); }

Explanation of the world's shortest IE decision if (!+[1,])