Reddit Comment Stream (Node.js)

reddit-comment-stream.js

module.exports = function() {

  let request = require("request-promise");
  let stopFlag;

  async function start() {
    if(!this.oncomment) {
      console.error("You must attach an oncomment handler (onerror handler is optional).");
      return;
    }
    stopFlag = false;
    while(1) {
      if(stopFlag) break;

      try {

        await sleep(1);

        let response = await request("https://www.reddit.com/r/all/comments/.json?limit=100");
        if(stopFlag) break;

        let newComments = extractNewComments(JSON.parse(response).data.children);
        for(let c of newComments) {
          this.oncomment(c);
        }

      } catch(e) {
        if(this.onerror) this.onerror(e);
      }

    }
  }

  function stop() {
    stopFlag = true;
  }

  return {
    start,
    stop
  }

}

async function sleep(delay) {
  return new Promise(resolve => setTimeout(resolve, delay*1000));
}


let oldCommentIds = [];
function extractNewComments(comments) {

  let newComments = [];
  for(let c of comments) {
    if(!oldCommentIds.includes(c.data.id)) {
      newComments.push(c.data);
      oldCommentIds.push(c.data.id);
    }
  }

  // don't let oldCommentIds grow too big
  if(oldCommentIds.length > 5000) {
    oldCommentIds = oldCommentIds.slice(2500); // cut off first half of array
  }

  return newComments;
}

test.js

// Use the above module as follows:
let RedditCommentStream = require('./reddit-comment-stream.js');
let stream = new RedditCommentStream();
stream.oncomment = function(comment) {
  console.log(comment);
}
stream.onerror = function(error) {
  console.log(error);
}
stream.start();

Note that this script isn't guaranteed to capture every single comment. If you've got a slow connection, or there's a sudden surge of activity on reddit, it may miss some comments. It's just a quick hacky script.