var max = 8;

    var sum = 0;

    var numbers = [];

​

    while (sum < max) {

      var number = Math.floor((Math.random() * 2) + 1);

      if (sum + number > max) {

        numbers.push(1);

        sum += 1;

      } else {

        numbers.push(number);

        sum += number;

      }

    }

​

console.log(numbers);