My userscript does not work

Question

I’m making a greasemonkey script but my code doesn’t work, I don’t know if it’s my browser, but if you find any error please fix it.

// ==UserScript==
// @name        ---
// @namespace   ---
// @description ---
// @author      ---
// @match       http://agar.io/*
// @version     1
// @grant       none
// ==/UserScript==

document.getElementsByClassName("btn btn-play btn-primary btn-needs-server")[0].innerHTML = "Jogar";
document.getElementsByClassName("btn btn-primary btn-success btn-freecoins")[0].innerHTML = "Moedas Grátis";
document.getElementsByClassName("btn btn-primary btn-shop")[0].innerHTML = "Loja";
document.getElementsByClassName("btn btn-warning btn-spectate btn-needs-server")[0].innerHTML = "Assistir";
document.getElementsByClassName("btn btn-danger btn-logout")[0].innerHTML = "Desconectar";
document.getElementsByClassName("btn btn-play-guest btn-success btn-needs-server")[0].innerHTML = "Jogar sem Conta";
document.getElementsByClassName("btn btn-warning btn-login-play btn-needs-server")[0].innerHTML = "Conectar";
document.getElementsByClassName("btn-text")[0].innerHTML = "Conectar com Facebook";
document.getElementsByClassName("btn-text")[1].innerHTML = "Conectar com Google";
document.getElementsByClassName("outlined-text")[0].innerHTML = "Conectando...";
document.getElementsByClassName("btn btn-info btn-copy-token copy-party-token")[0].innerHTML = "Copiar";
document.getElementById("create-party-btn").innerHTML = "Criar";
document.getElementById("joinPartyToken").placeholder = "Token da Party";
document.getElementById("join-party-btn").innerHTML = "Entrar";
document.getElementsByClassName("btn-donate")[0].innerHTML = "Doar por clique [Anúncio]";
document.getElementById("skin").placeholder = "URL da Skin (link direto)";
document.getElementById("clantag").placeholder = "TAG";

setInterval(repeat, 500);
function repeat{
    if (document.getElementsByClassName("agario-profile-name")[0].innerHTML == "Guest"){
        document.getElementsByClassName("agario-profile-name")[0].innerHTML = "Convidado";
    }
}

It opens agar.io with the szymy script (Ogar.io) and translates into English, but it does not work

Answer 1

You wrote the wrong function, missed relatives ():

function repeat{
    if (document.getElementsByClassName("agario-profile-name")[0].innerHTML == "Guest"){
        document.getElementsByClassName("agario-profile-name")[0].innerHTML = "Convidado";
    }
}

The correct is:

function repeat() {
    if (document.getElementsByClassName("agario-profile-name")[0].innerHTML == "Guest"){
        document.getElementsByClassName("agario-profile-name")[0].innerHTML = "Convidado";
    }
}

Answer 2

The main problem is because you are searching elements for multiple classes directly using document.getElementsByClassName. Use document.querySelector instead of this method.

And instead of using setInterval you can use the requestAnimFrame implemented in Agar.io code (yes, it is global):

requestAnimFrame(function repeat() {

    /* Mudanças nesse bloco */

    requestAnimFrame(repeat);

});

But I don’t know if updating the game’s HTML with an interval is the most efficient way, but the game’s code is a bit obfuscated and so it’s hard to figure that out...