Math

var random = Math.random() * 10;
random = random.toPrecision(3);
alert("Random: " + random);

var ceil = Math.ceil(random);
alert("Ceil: " + ceil);

var floor = Math.floor(random);
alert("Floor: " + floor);

var round = Math.round(random);
alert("Round: " + round);

The following JavaScript code generates a lotto number. 

var lotto = new Array();
var index = 0;
while(true) {
  var check = true;
  var ball = Math.random() * 45;
  ball = Math.floor(ball) + 1;
  for (var i = 0; i < lotto.length;i++) {
    if (lotto[i] == ball) {
      check = false;
      break;
    }
  }
  if (check) {
    lotto[index++] = ball
  }
  if (index > 5) {
    break;
  }
}

alert("Lotto number: " + lotto.toString());
References