生成一个session id

var genSessionId = function(length){
         var str = genSessionId.characters;
         if ( !"0"[0] ) { //fix IE67
             str = str.split("");
         }
         for(var i=0,id="",len = str.length;i < length;i++){
             id += str[Math.floor(Math.random() * len)];
         }
         return id;
     }
     genSessionId.characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';
     alert(genSessionId(24))

转自：https://www.cnblogs.com/rubylouvre/archive/2010/07/19/1780432.html