userscript are javascript script that are stored on the browser side and that can run:
// ==UserScript==
// @name Hello World
// @namespace https://datacadamia/
// @version 0.1
// @description Hello World
// @author Nico
// @match *://datacadamia.com/*/userscript
// @grant none
// ==/UserScript==
(function() {
'use strict';
// Your code here...
alert('This is the "Hello World UserScript script of datacadamia.com');
})();
To uniquely identify a user script
@name
@namespace
The pattern of match and exclude follows the match patterns of chrome extension
Example:
@match *://*/*
@match https://example.com/article/*
@exclude https://example.com/article/*/edit*
@require http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js
See how to edit script in your favorite editor (violentmonkey).