A simple notifications system for YCombinator Hacker News

hacker-news-notifications.user.js

// ==UserScript==
// @name        hacker-news-notifications
// @namespace   https://news.ycombinator.com/news
// @description Adds simple notifications to Hacker News
// @include     https://news.ycombinator.com/news
// @version     1
// @grant       none
// ==/UserScript==

/* NOTE: This script is run each time the user refreshes the page. */

/* Run main script */
check();

function check(){
  /* Check that storage is enabled */
  if(typeof(Storage) !== "undefined"){
  /* Initialise arrays */
    var current = [];
    var previous = [];
    /* Get the current state of the page */
    current = document.getElementsByClassName("storylink");
    /* Itterate over elements and test whether they have changed */
    for(var i = 0; i < current.length; i++){
      /* Get current state */
      var prev = window.sessionStorage.getItem(i);
      /* Has it changed? */
      if(prev != current[i].text){
        /* Update state before changing it */
        window.sessionStorage.setItem(i, current[i].text);
        /* Discover if we have just started this session */
        if(sessionAlive()){
          /* By default, say it moved up the rankings */
          current[i].style.color = "#0F0";
          /* Check to see if it actually moved down */
          for(var z = i - 1; z >= 0; z--){
            if(prev == current[z].text){
              /* It actually moved down the rankings because it exists above */
              current[i].style.color = "#F00";
              /* Break out of this loop, no more searching needed */
              break;
            }
          }
        }
      }
    }
    /* Update the fact this is a live session */
    setAlive();
  }else{
    /* Indicate there has been error silently in the console */
    err("Your browser doesn't support storage.");
  }
}

/**
 * sessionAlive()
 * 
 * Checks whether this is a new session or an old session.
 * 
 * @return True if old session, False is new session.
 **/
function sessionAlive(){
  /* Return the current state of the session */
  return window.sessionStorage.getItem("alive") == "true";
}

/**
 * setAlive()
 * 
 * Set the session status to be alive.
 **/
function setAlive(){
  window.sessionStorage.setItem("alive", "true");
}

/**
 * err()
 *
 * Displays a message in the console indicating there has been an error of some
 * kind.
 *
 * @param msg The message to be displayed.
 **/
function err(msg){
  console.log("hacker-news-notifications\n  [!!] " + msg);
}

hacker-news-notifications

Description

An extremely simple notifications system that tells you on a refresh whether a link has changed by highlighting it green (it has moved up a position) or red (it has moved down a position). All of the data is stored locally in your browser via the HTML5 storage capability and is deleted per session.

Example Output

Issues

If it doesn't appear to work then please check your console output as your browser may not be compatible. Please check this before raising a bug.

Known Bugs

None.

Bug fixes:

[X] Data is only stored for the session and not indefinitely as this seems somewhat irresponsible for user's space
[X] Newly added items at the bottom of the list appear green instead of red
[X] Check to see if the session is new - therefore no previous data exists and we cannot make judgement

Feature Request

[.] Background checking of the page (careful not to strain the server)
[.] Desktop notifications
[.] Tracking of comments and replys