separate numbers with commas

gistfile1.txt

def separate_comma(number)
results = number.to_s.split("")
reverse_counter = results.length - 1
output = ""
comma_counter = 0
results.length.times do |i|
    output = results[reverse_counter] + output
    reverse_counter = reverse_counter - 1
    comma_counter = comma_counter + 1
        if comma_counter%3 == 0 && comma_counter/number.to_s.length != 1
                output = "," + output
        else
        end
end
output
end