debugmode.js

// ==UserScript==
// @name         [DEBUG MODE]
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Library for calling a callback if debug cookie has been set
// @author       You
// @include      *
// @grant        none
// ==/UserScript==

(function( fn , args ) {
    'use strict';
    let if_debug_mode;
    const func_observer = (function(mutations){
        console.log(mutations);
    });

    if_debug_mode = (function( fn, args = [] ){
        let pat = new RegExp('[^\w]debug=true[$|;]');
        if(pat.test(document.cookie))
        {
            try {
                callback.apply( null , args )
            } catch(e){console.error(e);}
        }
    })();
})( fn , args );