invidious/assets/js/subscribe_widget.js

"use strict";
var subscribe_data = JSON.parse(
  document.getElementById("subscribe_data").textContent,
);
var payload = "csrf_token=" + subscribe_data.csrf_token;

var subscribe_button = document.getElementById("subscribe");

if (subscribe_button.getAttribute("data-type") === "subscribe") {
  subscribe_button.onclick = subscribe;
} else {
  subscribe_button.onclick = unsubscribe;
}

function toggleSubscribeButton() {
  subscribe_button.classList.remove("primary");
  subscribe_button.classList.remove("secondary");
  subscribe_button.classList.remove("unsubscribe");
  subscribe_button.classList.remove("subscribe");

  if (subscribe_button.getAttribute("data-type") === "subscribe") {
    subscribe_button.textContent =
      subscribe_data.unsubscribe_text + " | " + subscribe_data.sub_count_text;
    subscribe_button.onclick = unsubscribe;
    subscribe_button.classList.add("secondary");
    subscribe_button.classList.add("unsubscribe");
  } else {
    subscribe_button.textContent =
      subscribe_data.subscribe_text + " | " + subscribe_data.sub_count_text;
    subscribe_button.onclick = subscribe;
    subscribe_button.classList.add("primary");
    subscribe_button.classList.add("subscribe");
  }
}

function subscribe(e) {
  e.preventDefault();
  var fallback = subscribe_button.textContent;
  toggleSubscribeButton();

  var url =
    "/subscription_ajax?action=create_subscription_to_channel&redirect=false" +
    "&c=" +
    subscribe_data.ucid;

  helpers.xhr(
    "POST",
    url,
    { payload: payload, retries: 5, entity_name: "subscribe request" },
    {
      onNon200: function (xhr) {
        subscribe_button.onclick = subscribe;
        subscribe_button.textContent = fallback;
      },
    },
  );
}

function unsubscribe(e) {
  e.preventDefault();
  var fallback = subscribe_button.textContent;
  toggleSubscribeButton();

  var url =
    "/subscription_ajax?action=remove_subscriptions&redirect=false" +
    "&c=" +
    subscribe_data.ucid;

  helpers.xhr(
    "POST",
    url,
    { payload: payload, retries: 5, entity_name: "unsubscribe request" },
    {
      onNon200: function (xhr) {
        subscribe_button.onclick = unsubscribe;
        subscribe_button.textContent = fallback;
      },
    },
  );
}