[ruslan_mart]

По совету Рони

function rand(max) {
   var val = Math.floor(Math.random() * (max + 1));
   if(val in rand.tmp) return rand(max);
   rand.tmp[val] = true;
   return val;
}

rand.tmp = {};


alert( rand(100) );
alert( rand(100) );
alert( rand(100) );
alert( rand(100) );
alert( rand(100) );