The following manipluations are performed in this order:

1. replace slashes / \ and spaces with dashes -
2. replace any accented characters with their closest non-accented equvalent, e.g. é becomes e
3. remove all non-alphanumeric characters (anything other than A-Z, a-z, 0-9, and -)
4. replace multiple consecutive dashes --- with a single dash -
5. remove leading dashes, e.g. -Gengar- becomes Gengar-
6. remove trailing dashes, e.g. Gengar- becomes Gengar
7. convert to lowercase, e.g. Gengar becomes gengar

This module relies on the Lua utf-8 library which should be built into Lua, but isn't always. You've been warned!

local sluggify = require("sluggify")
local slug = sluggify.sluggify("Pokémon Blue!")
print(slug)
assert(slug == "pokemon-blue") -- expected output

pokemon-blue

This was originally written for my Lospec Palette Importer Aseprite extension, but I thought it might be useful on its own.

Thanks to Sam Keddy for the inspiration!