<script>
function setRand(min,max,number) {
    randResult = new Array();
    randList = new Array();
    for(i = min; i <= max; i++) {
    randList.push(i);
    }

    for(i = 0; i < number; i++) {
    getRand();
    }
    alert(randResult);
}

function getRand() {
    randNumber = Math.floor(Math.random() * randList.length);
    randResult.push(randList[randNumber]);
    randList.splice(randNumber,1);
}

//Min, Max, Number
setRand(7,10,3);
</script>

출처 : phpschool