EHShortcut.user.js

// ==UserScript==
// @name        EHShortcut
// @namespace   FlandreDaisuki
// @include     http://exhentai.org/*
// @include     http://g.e-hentai.org/*
// @version     2016.03.02
// @grant       GM_addStyle
// ==/UserScript==

GM_addStyle(`
    html, body {
        height: 100%;
    }

    .EHSRoot {
        margin: 0px 0px 0px 20px;
        cursor: pointer;
    }

    .EHSFS{
        height: 100px;
        width: 100px;
        border: 1px solid black;
        background-color: rgb(79, 83, 91);
    }

    .EHSFSB{
        position: fixed;
        top: 0px;
        left: 0px;
        height: 100vh;
        width: 100%;
        background-color: rgba(0, 0, 0, 0.4);
        display: flex;
        z-index: 2;
        align-items: center;
        justify-content: center;
    }

    .EHSFSB.hidden {
        visibility: hidden;
    }
`);

function RemoveUrlPage(url) {
    var [umatch, upath, usearch] = url.match(/https?:\/\/[^\/]*(?:([^?]*)(.*))/);
    if (upath === '/') {
        return RemoveUrlParameter(umatch, ['page']);
    } else {
        return umatch.replace(/\d+$/, '');
    }
}

function RemoveUrlParameter(url, rmParameters) {
    var [umatch, upath, uparameter] = url.match(/([^\?]*)\?(.*)/);
    var uparas = uparameter.split('&');

    var resParas = uparas.filter((p) => {
        return rmParameters.every((rp) => {
            return p.indexOf(rp + '=') !== 0;
        });
    });

    if (resParas.length > 0) {
        return `${upath}?${resParas.join('&')}`;
    } else {
        return upath;
    }
}

function Elem(tagName, options) {
    var elem = document.createElement(tagName);
    for (let opt of Object.keys(options)) {
        elem[opt] = options[opt];
    }
    return elem;
}

var nb = document.querySelector('#nb');
var EHSRoot = Elem('a', {
    className: 'EHSRoot',
    innerHTML: 'Shortcuts'
});
nb.appendChild(EHSRoot);

var EHSFSB = Elem('div', {
    className: 'EHSFSB hidden'
});
var EHSFS = Elem('div', {
    className: 'EHSFS'
});
document.body.appendChild(EHSFSB);
EHSFSB.appendChild(EHSFS);

EHSFSB.addEventListener('click', function() {
    EHSFSB.classList.add('hidden');
});

EHSFS.addEventListener('click', function(event) {
    event.stopPropagation(); //remove bubbling
});

EHSRoot.addEventListener('click', function() {
    EHSFSB.classList.remove('hidden');
});