public function randString(_length:Number = 10):String{
			var alphabet:String = "qwertyuiopasdfghjklzxcvbnm123456789QWERTYUIOPASDFGHJKLZXCVBNM";
			var temp:Array = alphabet.split("");
			var tempString:String = "";
			
			for(var i:Number = 0; i<_length; i++){
				tempString+= temp[ Math.ceil( Math.random()*alphabet.length - 1 )]
			}
			
			return tempString;
		}

This is easy way to generate random string

this will generate random word with 10 letters in it
var a:String = randString(10);

Random generated String

ActionScript 3