A bookmarklet I wrote to automatically transfer Lemmy subscriptions to other instances.

bookmarklet.js

javascript: (async function () {
  const currentURL = window.location.href;
  const currentHostname = window.location.hostname;
  if (!currentURL.includes("listing_type/Subscribed/page")) {
    window.alert("Not in the current page. Redirecting..");
    window.location.href = `communities/listing_type/Subscribed/page/1`;
  }
  const table = document.getElementById("community_table");
  const anchorTags = table.getElementsByTagName("a");
  const titles = [];
  for (let i = 0; i < anchorTags.length; i++) {
    let title = anchorTags[i].title.substring(1);
    if (!title.includes("@")) {
      title += `@${currentHostname}`;
    }
    titles.push(title);
  }

  var instancePrompt = window.prompt("Please enter what instance you want to add the bookmarks to: (lemmy.ml, lemmy.world, beehaw.org, etc.)", "");
  if (!instancePrompt) {
    alert("Please input your preferred instance!");
    return;
  }

  var emailInput = window.prompt("Please enter your username or email:", "");
  if (!emailInput) {
    alert("Please input your email or email!");
    return;
  }
  var passwordInput = window.prompt("Please enter your password:", "");
  if (!passwordInput) {
    alert("Please input your password!");
    return;
  }
  const baseURL = `https://cors-anywhere.herokuapp.com/https://${instancePrompt.toLowerCase()}/api/v3`;
  let loginForm = {
    username_or_email: emailInput,
    password: passwordInput,
  };
  try {
    var jwt = await fetch(`${baseURL}/user/login`, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        "access-control-allow-origin": "*",
      },
      body: JSON.stringify(loginForm),
    });
  } catch (err) {
    console.log(err);
    alert("Visit https://cors-anywhere.herokuapp.com/corsdemo and click on 'participate in demo' then try again");
    return;
  }
  if (jwt.ok === false) {
    if (jwt.status === 429) {
      alert("Too many requests from this IP, try again.");
      return;
    }
    jwt = await jwt.json();
    if (jwt.error === "no t_logged_in") {
      alert("Invalid login, please make sure your credentials are correct and try again.");
      return;
    }
  } else {
    jwt = await jwt.json();
    jwt = jwt.jwt;
  }

  let failedRequests = [];
  for (const community of titles) {
    const postForm = {
      auth: jwt,
      name: community,
    };
    const queryParams = new URLSearchParams(postForm);

    let requestedCommunity = await fetch(`${baseURL}/community?${queryParams}`, {
      method: "GET",
      headers: {
        "Content-Type": "application/json",
      },
    });
    if (!requestedCommunity.statusText === "OK") {
      failedRequests.push(community);
      continue;
    }
    requestedCommunity = await requestedCommunity.json();
    const communityID = requestedCommunity?.community_view?.community?.id;

    const subscribeForm = {
      auth: jwt,
      community_id: communityID,
      follow: true,
    };
    if (!communityID) {
      fetch(`${baseURL}/community/follow`, {
        method: "POST",
        headers: {
          "Content-Type": "application/json",
        },
        body: JSON.stringify(subscribeForm),
      }).then(() => console.log(`subscribed to ${requestedCommunity?.community_view?.community?.name} in ${instancePrompt}`));
    }
  }
  if (failedRequests.length > 0) {
    alert(`Done, but some of the communities gave errors, most likely because they've been blocked by your instance, here's a list of them:\n${failedRequests.join("\n")}`);
  } else {
    alert("Done!");
  }
})();