code: function multiplyInteger(x, k) {
        var temp,
          carry = 0,
          i = x.length;
  
        for (x = x.slice(); i--;) {
          temp = x[i] * k + carry;
          x[i] = temp % BASE | 0;
          carry = temp / BASE | 0;
        }
  
        if (carry) x.unshift(carry);
  
        return x;
      }
docs: Assumes non-zero x and k, and hence non-zero result.