Convert emoji and codepoints each other in Ruby

The tips below are what I've learned while implementing a gem, github_reactions, to summarize reactions on GitHub issues and pull requests.

Get codepoints from emoji

"👍".unpack("U*")
=> [128077]

"👍".codepoints
=> [128077]

# Convert to hexadecimal
"👍".each_codepoint.map {|n| n.to_s(16) }
=> ["1f44d"]

Get emoji from codepoints

[128077].pack("U*")
=> "👍"

0x1f44d.chr('UTF-8')
=> "👍"

"\u{1f44d}"
=> "👍"