Restore GameFAQs Board Nav Buttons

// ==UserScript==
// @name        Board Navigation Buttons
// @namespace   GameFAQs
// @description Restore the board navigation buttons, and add an AMP button
// @include     /http://www\.gamefaqs\.com/boards/[0-9][0-9]*/
// @grant       none
// @version     1.0
// @author      Frost_shock_FTW
// ==/UserScript==

var paginate_button_lists = document.getElementsByClassName( 'paginate user' );

var topiclist_button = document.createElement( 'li' );
var topiclist_link = document.createElement( 'a' );
var topiclist_text = document.createTextNode( 'Topic List' );

topiclist_link.appendChild( topiclist_text );
topiclist_link.href = Get_topic_list_url();
topiclist_button.appendChild( topiclist_link );

var boardlist_button = document.createElement( 'li' );
var boardlist_link = document.createElement( 'a' );
var boardlist_text = document.createTextNode( 'Board List' );

boardlist_link.appendChild( boardlist_text );
boardlist_link.href = Get_board_list_url();
boardlist_button.appendChild( boardlist_link );

var amp_button = document.createElement( 'li' );
var amp_link = document.createElement( 'a' );
var amp_text = document.createTextNode( 'Active Messages Posted' );

amp_link.appendChild( amp_text );
amp_link.href = '/boards/myposts.php';
amp_button.appendChild( amp_link );

// This script runs on board pages and topic pages.
// Only insert a Topic List button if we are on a topic page.
var on_topic_page = document.getElementsByClassName( 'board topics tlist' ).length == 0;

for( var i = 0; i < paginate_button_lists.length; ++i ) {
    if ( on_topic_page ) {
        paginate_button_lists[i].insertBefore( topiclist_button.cloneNode( true ),
                                               paginate_button_lists[i].children[1] );
    }

    paginate_button_lists[i].insertBefore( boardlist_button.cloneNode( true ),
                                           paginate_button_lists[i].children[1] );

    paginate_button_lists[i].insertBefore( amp_button.cloneNode( true ),
                                           paginate_button_lists[i].children[1] );
}

function Get_board_list_url() {
    return window.location.origin + '/boards';
}

function Get_topic_list_url() {
    // A GameFAQs topic post link will be in one of two forms:
    // - http://www.gamefaqs.com/boards/BOARDID-BOARD-NAME/TOPICID#POSTNUM
    // - http://www.gamefaqs.com/boards/BOARDID-BOARD-NAME/TOPICID?page=PAGENUM#POSTNUM
    //
    // In both cases, the topic list URL can be found by truncating before the last '/'

    var last_slash_index = window.location.href.lastIndexOf( '/' );

    return window.location.href.slice( 0, last_slash_index );
}