RegExp Test

JavaScript

var text = " ";
    var numChars = "0123456789";
    var upCaseChars="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    var lowCaseChars="abcdefghijklmnopqrstuvwxyz";

    for( var i=0; i < 4; i++ )
    {  
        text += numChars.charAt(Math.floor(Math.random() * numChars.length));
        text += upCaseChars.charAt(Math.floor(Math.random() * upCaseChars.length));
        text += lowCaseChars.charAt(Math.floor(Math.random() * lowCaseChars.length));
    }
    alert (text);