HyperScript
Docs

Quick tutorial

A script is a text file in plugins/HyperScript/scripts/. This one adds a command, reacts to an event, and remembers something about each player. Create the file plugins/HyperScript/scripts/hello.hs with this in it:

command /hello:
    description: Say hello and count how often you have
    trigger:
        add 1 to {%player%.hellos}
        send "&aHello, %player.name%! You have said hello %{%player%.hellos}% times."

on player join:
    send "&7Type &f/hello &7to try your first script."

Save it. A moment later the console reports that the script was loaded, and /hello works in game. What each part does:

Now give the command something to hand out, at most once a day:

command /daily:
    cooldown: 1 day
    trigger:
        give 3 diamond to player
        send title "&6Daily reward!" with subtitle "&e+3 diamonds" to player

Add that to the same file and save again. If you make a mistake, such as a missing quote, the error names the file and line and the rest of your scripts keep running.

That is the whole workflow: edit, save, try. Everything else the language can do, from GUIs and scoreboards to web requests, is listed on the Docs page, where you can filter by topic and search as you type.