BOJ Group Practice Tier

script.js

// ==UserScript==
// @name        BOJ Group Practice Tier
// @namespace   Violentmonkey Scripts
// @match       https://www.acmicpc.net/group/practice/view/*
// @grant       GM_xmlhttpRequest
// @version     1.0
// @author      kiwiyou
// ==/UserScript==
const problemAnchors = document.querySelectorAll('a[href^="/problem/"]');
const problemMap = new Map();
for (const anchor of problemAnchors) {
  const groups = anchor.href.match(/\/problem\/(\d+)$/);
  if (groups === null) {
    continue;
  }
  const key = +groups[1];
  const list = problemMap.get(key);
  if (!list) {
    problemMap.set(key, [anchor]);
  } else {
    list.push(anchor);
  }
}
const request = GM_xmlhttpRequest({
  url: `https://solved.ac/api/v3/problem/lookup?problemIds=${[...problemMap.keys()].join(",")}`,
  method: 'GET',
  responseType: 'json',
  onloadend(res) {
    if (res.response === null) {
      return;
    }
    for (const { problemId, level } of res.response) {
      for (const anchor of problemMap.get(problemId)) {
        const tier = document.createElement('img');
        tier.src = `https://static.solved.ac/tier_small/${level}.svg`;
        const computedStyle = window.getComputedStyle(anchor, null);
        const fontSize = computedStyle.getPropertyValue('font-size');
        tier.style = `height: calc(${fontSize} * 1.2); margin-right: calc(${fontSize} * 0.5);`;
        anchor.prepend(tier);
      }
    }
  },
})