🦕 Running your first Deno script (From: https://www.edoardoscibona.com/running-your-first-deno-script)

main.ts

//
// Follow along with the article at:
// https://www.edoardoscibona.com/running-your-first-deno-script
//
// This script is licensed under the MIT license (https://opensource.org/licenses/MIT).
//

// Import the `sleep` function from a remote module
import { sleep } from "https://deno.land/x/sleep/mod.ts";

/** Base URL for all calls to the Hacker News API */
const baseURL = "https://hacker-news.firebaseio.com/v0";

/** Item represents an item fetched from the HN API */
interface Item {
  /** Unique item ID; the only required property */
  readonly id: number;
  /** Item type (`job`, `story`, `comment`, `poll`, or `pollopt`) */
  readonly type?: string;
  /** Username of the user who submitted the item */
  readonly by?: string;
  /** Title text for a story, poll or job */
  readonly title?: string;
  /** URL for a story or job */
  readonly url?: string;
  /** Text for a story, comment, poll, poll option or job */
  readonly text?: string;
  /** Unix timestamp for when the item was created */
  readonly time?: number;
  /** Score for a story, job or poll; votes for a poll option */
  readonly score?: number;
  /** Number of total comments for a story or poll */
  readonly descendants?: number;
  /** Set to `true` if the item is deleted */
  readonly deleted?: boolean;
  /** Set to `true` if the item is dead */
  readonly dead?: boolean;
  /** ID of the parent item of a comment (a story or another comment) */
  readonly parent?: number;
  /** List of IDs of the item's comments, in display order */
  readonly kids?: number[];
  /** ID of the poll associated to a poll option */
  readonly poll?: number;
  /** List of IDs of related poll options, in display order */
  readonly parts?: number[];
}

/** getMaxItemID returns the ID of the most recent item published on HN */
async function getMaxItemID(): Promise<number> {
  const endpoint = `${baseURL}/maxitem.json`;
  const res = await fetch(endpoint);
  const id = await res.json();
  return id;
}

/** getItemByID fetches an item from the HN API given its ID */
async function getItemByID(id: number): Promise<Item | undefined> {
  const endpoint = `${baseURL}/item/${id}.json`;
  const res = await fetch(endpoint);
  const item = await res.json();
  return item ?? undefined;
}

/** streamComments continuously fetches and displays the most recent comments published on HN */
async function streamComments() {
  // Get the ID of the most recent item
  let id = await getMaxItemID();

  // Keep running forever
  while (true) {
    // Get the item
    const item = await getItemByID(id);

    // If the item does not exist, wait 5 seconds and try again
    if (!item) {
      await sleep(5);
      continue;
    }

    // Print only items that are visible comments
    const { type, deleted, dead } = item;
    const removed = deleted || dead || false;
    if (type === "comment" && !removed) {
      // Get the comment's author, if any
      const author = item.by ?? "unknown author";

      // Get the comment's URL on HN website
      const hnURL = `https://news.ycombinator.com/item?id=${id}`;

      // Print the comment
      console.log(`\nRead new comment by ${author} on ${hnURL}`);
      console.log(item);
    }

    // Increment the ID for the next item
    id += 1;
  }
}

await streamComments();