require "js"

response = JS.global.fetch("<dumped buffer's url>").await
puts response[:status]

arraybuffer = response.arrayBuffer.await

# Expected goal:
#   Marshal.load(arraybuffer)

# Correct but too slow way:
uint8array = JS.global[:Uint8Array].new(arraybuffer)
Marshal.load(uint8array.to_a.map(&:to_i).pack("C*")) # Especially the slow JS::Object#to_i on each byte.