happend LUA script for redis

happend.js

const Redis = require('ioredis')
const redis = new Redis()

redis.defineCommand("happend", {
    numberOfKeys: 2,
    lua: `
        local current = redis.call("hget", KEYS[1], KEYS[2])
        if current == nil or current == false then
            current = ARGV[1]
        else
            current = current .. ARGV[1]
        end

        redis.call("hset", KEYS[1], KEYS[2], current)

        return #current
    `,
});

(async () => {
  let newLength = await redis.happend('key', 'sub-key', 'value')
})()

happend.lua

local current = redis.call("hget", KEYS[1], KEYS[2])
if current == nil or current == false then
    current = ARGV[1]
else
    current = current .. ARGV[1]
end

redis.call("hset", KEYS[1], KEYS[2], current)

return #current