modify array with << and delete instead of + and -

array_mod_benchmark.rb

ATTRIBUTES = %w{a b c d e f g h i j _id}

t0 = Time.now

100_000.times do
  ATTRIBUTES.dup.map { |k| k.to_s } + ['id'] - ['_id']
end

map_time = Time.now - t0

t1 = Time.now

100_000.times do
  acc = []
  ATTRIBUTES.dup.each { |k| acc << k.to_s }
  acc << 'id'
  acc.delete('_id')
  acc
end

each_time = Time.now - t1

savings_ratio = (map_time - each_time).to_f / map_time

puts "You saved #{"%.2f" % (savings_ratio * 100)}%"