Greasy Fork

// ==UserScript==
// @name Opium Pulses giveaway Auto join
// @namespace Opium Pulses auto
// @author SaddestPanda
// @description Opium Pulses giveaway Auto joiner
// @match http*://www.opiumpulses.com/giveaways*
// @homepage https://greasyfork.org/en/scripts/19858-opium-pulses-giveaway-auto-join
// @supportURL https://greasyfork.org/en/scripts/19858-opium-pulses-giveaway-auto-join/feedback
// @version 3.5
// @grant none
// ==/UserScript==

var timehelper = 0;
var thelength = $(".giveaways-page-item").length;
var giveaways = $(".giveaways-page-item");

for (var i = 0; i < thelength; i++) {
if (giveaways[i].innerHTML.indexOf("ENTERED") == -1) {
if (giveaways[i].innerHTML.indexOf("FREE") != -1) {
JoinGA(giveaways[i].querySelector(".giveaways-page-item-img-btn-enter").href);
}
}
}

function JoinGA(hreflink) {
setTimeout(function () {
$.post(hreflink);
console.log("Entered giveaway: " + hreflink);
console.log("This script is deprecated. It will not be updated anymore.");
}, Math.floor((timehelper * 450) + 450));
timehelper++;
}

I reworked the script a little bit and now it works)