foo.js

//If inputData.rawMessage does not contain "just signed" - abort
if (!inputData.rawMessage.includes("just signed")) {
  return;
}

const emojis = [
  "rocket",
  "success",
  "tada",
  "v",
  "star",
  "star-struck",
  "fire",
  "boom",
  "party_blob",
];
// Randomly choose 2 to 5 emojis
const numberOfEmojis = Math.floor(Math.random() * 3) + 2;

const selectedEmojis = [];
for (let i = 0; i < numberOfEmojis; i++) {
  const randomIndex = Math.floor(Math.random() * emojis.length);
  selectedEmojis.push(emojis[randomIndex]);
}

async function reactToMessage(emoji) {
  var response = await fetch("https://slack.com/api/reactions.add", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: "Bearer " + inputData.slackAuthToken,
    } /*  */,
    body: JSON.stringify({
      channel: inputData.channelId,
      name: emoji,
      timestamp: inputData.timestamp,
    }),
  });

  return response.json();
}

for (let i = 0; i < selectedEmojis.length; i++) {
  await reactToMessage(selectedEmojis[i]);
}

callback(null, {
  selectedEmojis: selectedEmojis,
  message: inputData.rawMessage,
});