Oldpage Bets Maker

// ==UserScript==
// @name         Oldpage Bets Maker
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Allows user to generate a code to share with others that will place the same bets
// @author       KK20
// @match        http://neofoodclub.fr/oldpage.html*
// @require      https://code.jquery.com/jquery-3.1.0.min.js
// @grant        none
// ==/UserScript==

this.$ = this.jQuery = jQuery.noConflict(true);

function place_bets() {
    var bet_num, arena, pirate, substr_bet;

    var bet_code = $("input#bet_textarea").val();
    if (bet_code.length % 5 != 0) {
        alert("This is an invalid bet code! Please check that you copied it right.");
        return;
    }

    for(bet_num = 0; bet_num < bet_code.length / 5; bet_num++) {
        substr_bet = bet_code.substring(bet_num * 5, bet_num * 5 + 5);
        for(arena = 0; arena < 5; arena++) {
            pirate = substr_bet[arena];
            check_radio(arena, pirate, bet_num);
        }
    }
}

function make_bet_code() {
    var bets = Array(10).fill("");
    $("input:radio").each(function(index, radio) {
        if ($(this).is(":checked"))
            bets[index % 10] += Math.floor(index % 50 / 10);
    });
    $("input#bet_textarea").val(bets.join(""));
}

function check_radio(arena_id, pirate_row, bet_number) {
    $("tbody:eq("+arena_id+") tr:eq("+pirate_row+") input:radio:eq("+(bet_number)+")").prop("checked", true).trigger("click");
}

$("div#el a:first").after('<br><input id="bet_textarea" type="textbox"><input id="bet_submit" type="button" value="Place Bets!"><input id="gen_code" type="button" value="Generate Code">');
$("input#bet_submit").on("click", place_bets);
$("input#gen_code").on("click", make_bet_code);