Display Hacker News user karma next to usernames using the HN Firebase API, with caching, rate limiting.

HN Script - Show karma of users next to usernames.md

Show karma of users next to usernames on hn.

karma.user.js

// ==UserScript==
// @name         Hacker News – Display user karma next to usernames
// @version      1.0
// @description  Display Hacker News user karma next to usernames using the HN Firebase API, cache results 1d.
// @homepageURL  https://gist.github.com/corentinbettiol/289503b4033a788df91fbc2bc5a3f742#file-karma-user-js
// @match        https://news.ycombinator.com/*
// @grant        GM.getValue
// @grant        GM.setValue
// @grant        GM.xmlHttpRequest
// @connect      hacker-news.firebaseio.com
// ==/UserScript==

(async () => {
    'use strict';

    const API = 'https://hacker-news.firebaseio.com/v0/user/';
    const TTL = 86400000; // 1d

    const sleep = ms => new Promise(r => setTimeout(r, ms));

    const getKarma = username => new Promise((resolve, reject) => {
        GM.xmlHttpRequest({
            method: 'GET',
            url: `${API}${username}.json`,
            onload: r => {
                try {
                    const data = JSON.parse(r.responseText);
                    resolve(data?.karma ?? null);
                } catch { reject(); }
            },
            onerror: reject
        });
    });

    const getCached = async u => {
        const e = await GM.getValue(u);
        return (e && Date.now() - e.t < TTL) ? e.k : null;
    };

    const setCached = (u, k) =>
        GM.setValue(u, { k, t: Date.now() });

    const styleKarma = (span, karma) => {
        const k = Math.log10(karma + 1);

        // color (log scale tiers)
        span.style.color =
            k < 2 ? '#bbb' :
            k < 3 ? '#999' :
            k < 4 ? '#cc8400' :
            k < 4.5 ? '#ff8800' :
            '#ff6600';

        // glow
        if (karma > 50000) {
            span.style.textShadow =
                '0 0 8px #ffd700, 0 0 16px rgba(255,215,0,0.6)';
        } else if (karma > 1500) {
            const t = Math.min(karma, 30000) / 30000;
            span.style.textShadow =
                `0 0 ${1 + 4*t}px rgba(255,102,0,${0.15 + 0.25*t})`;
        }
    };

    const links = [...document.querySelectorAll('a[href^="user?id="]')];
    const users = {};

    for (const link of links) {
        const u = link.textContent.trim();
        if (!u) continue;
        (users[u] ??= []).push(link);
    }

    for (const username of Object.keys(users)) {

        let karma = await getCached(username);

        if (karma === null) {
            try {
                karma = await getKarma(username);
                if (typeof karma === 'number')
                    await setCached(username, karma);
            } catch { continue; }
        }

        if (typeof karma !== 'number') continue;

        for (const el of users[username]) {
            if (el.dataset.karma) continue;
            el.dataset.karma = 1;

            const span = document.createElement('span');
            span.textContent = ` (${karma})`;
            span.style.fontSize = '0.85em';
            span.style.marginLeft = '2px';

            styleKarma(span, karma);
            el.after(span);
        }
    }
})();

LICENSE

           DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                   Version 2, December 2004

Copyright (C) 2004 Sam Hocevar <sam@hocevar.net>

Everyone is permitted to copy and distribute verbatim or modified
copies of this license document, and changing it is allowed as long
as the name is changed.

           DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
  TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

 0. You just DO WHAT THE FUCK YOU WANT TO.