collection

collection

numbers = [1, 2, 3, 4, 5, 6]

result1 = []
numbers.each do |num|
  result1 << num * 2 if num % 2 == 0
end

p result1  # => [4, 8, 12]

numbers.select{|num| num % 2 == 0 }.map{|num| num * 2 } # => [4, 8, 12]
numbers.inject([]) {|result2, num| result2 << num * 2 if num % 2 == 0; result2 } #=> [4, 8, 12]
numbers.inject([]) {|result2, num| result2.tap {|r| r << num * 2 if num % 2 == 0 } } #=> [4, 8, 12]