random message with no repeats

im trying to display a random number, but each time a button is pressed that calls the test function, i don't want to random number to be repeated. i know i have to declare 2 variables and a while loop, but i'm stuck as to what to put in the second variable and in the while loop. any advice is appreciated

var random = Math.floor(Q * Math.random());
var random2 = ??

function test () {
document.write(random);

while (random == random2) {
document.write(random);
}
}

 

erm. this is interesting... just wrote this which will try to generate a unique number from a set until it runs out of such. eg, if params are 10, 20 - it will produce a single number between 10 and 20 (inclusive of 10 and 20) and give up after 11 iterations.

var $rnd = {
    used: [],
    unique: function(min, max) {
        var unique = false, expired = false, cap = max - min + 1, done = 0;

        if (cap < 0)
            return;

        while(!unique) {
            var randomNo = min + Math.floor(cap * Math.random());

            if (!this.used[randomNo]) {
                this.used[randomNo] = true;
                unique = true;
            }
            else {
                done++;
            }

            if (done > cap)
                unique = expired = true;

        }
        return (expired) ? null : randomNo;
    }
};

imaginaryButton.onclick = function() {
    // important, function will retrun null if it can't find a unique number anymore (after 11 clicks)
    var foo = $rnd.unique(10, 20), bar = (foo === null) ? "sorry all numbers run out!" : foo; 
    alert(bar);
};

Code (javascript):

 

hi, try below code:

var random2 = [];

function test(random2, Q) {
	var Q = Q || 100;
	var random = Math.floor(Q * Math.random());
	if (random2.toString().indexOf(random+' ') == -1) {
		random2.push(random+' ');
		//alert('Your unique message here... with random number: '+random);
	}
	return random2;
}

//call test function as many times as You want
for (var i=1; i<100; i++) {
	random2 = test(random2);
}
//document.write(random2.join(' ; '));

//Alternatively You can assign onclick event to Your button instead of using for loop statement
//but then remeber to uncomment alert message call inside test function and 
//of course please comment for loop statement
<a href="#" onclick="javascript:random2 = test(random2);">give me unique message</a>

Code (markup):

 

Do you not want the number to be repeated at all (while possible)? or do you not want the number to be repeated twice in a row?