ci: lint with ESLint and fix what it surfaced

.github/workflows/ci.yml

@@ -30,6 +30,7 @@ jobs:
       - run: npm ci --no-audit --no-fund
       - run: npm test
       - run: npm run typecheck
+      - run: npm run lint
       # --check builds twice and fails when the two outputs differ
       - run: node scripts/build.mjs --check
       - name: Package contents

.github/workflows/release.yml

@@ -31,6 +31,7 @@ jobs:
       - run: npm ci --no-audit --no-fund
       - run: npm test
       - run: npm run typecheck
+      - run: npm run lint
       - run: node scripts/build.mjs --check
 
       - name: Check the tag against package.json

CONTRIBUTING.md

@@ -12,12 +12,14 @@ data is outside this repository.
 
 ## Development
 
-Node.js 22 or later. There are no runtime dependencies; the development dependencies are esbuild and TypeScript.
+Node.js 22 or later. There are no runtime dependencies; the development dependencies are esbuild, TypeScript and
+ESLint.
 
 ```sh
 npm ci
 npm test               # unit tests: node --test tests/unit/*.test.mjs
 npm run typecheck      # type-checks tests/types/ against types/
+npm run lint           # ESLint's recommended rules (eslint.config.js)
 npm run build          # dist/: ESM, minified ESM and IIFE bundles with source maps
 node scripts/build.mjs --check   # builds twice and fails if the outputs differ
 ```

README.en.md

@@ -232,6 +232,7 @@ npm ci
 npm test                  # unit tests (node --test, synthetic inputs only)
 npm run build             # browser bundles in dist/
 npm run typecheck         # checks the type declarations in types/
+npm run lint              # ESLint (eslint.config.js)
 npm run validate-data -- <site dir> [chart id ...]              # validates a site against the data format
 node scripts/story-author.mjs help                              # the commands of the story script tool (experimental)
 OURNOTES_DATA=<site dir> npm run test:data                      # opt-in: runs the player in Node on real chart data

README.md

@@ -181,6 +181,7 @@ npm ci
 npm test                  # 单元测试（node --test，仅使用合成输入）
 npm run build             # 构建 dist/ 下的浏览器包
 npm run typecheck         # 检查 types/ 下的类型声明
+npm run lint              # ESLint 检查（eslint.config.js）
 npm run validate-data -- <站点目录> [谱面 id ...]              # 按数据格式校验一个站点
 node scripts/story-author.mjs help                             # 自写剧情工具（实验功能）的命令
 OURNOTES_DATA=<站点目录> npm run test:data                     # 可选：用真实谱面数据在 Node 中运行播放器

eslint.config.js

@@ -0,0 +1,25 @@
+// ESLint: the recommended rules over the sources, scripts, examples and tests (`npm run lint`). The player runs in
+// browsers, the scripts and tests in Node.js; the Live2D and Spine runtimes are page scripts that define globals.
+// The ports keep the statement order of the code they reproduce, including assignments a later branch overwrites, so
+// no-useless-assignment is off.
+import js from "@eslint/js";
+import globals from "globals";
+
+export default [
+  { ignores: ["dist/"] },
+  js.configs.recommended,
+  {
+    languageOptions: {
+      ecmaVersion: 2024,
+      sourceType: "module",
+      globals: {
+        ...globals.browser, ...globals.node,
+        Live2DCubismCore: "readonly", Live2DCubismMotionSyncCore: "readonly", spine: "readonly",
+      },
+    },
+    rules: {
+      "no-unused-vars": ["error", { args: "none", caughtErrors: "none", ignoreRestSiblings: true }],
+      "no-useless-assignment": "off",
+    },
+  },
+];

examples/songs/songs.js

@@ -283,8 +283,7 @@ const main = async () => {
   // the route heading: the view's title and what it answers
   const renderHead = () => {
     const t = u();
-    const [title, lead] = S.view === "guide" ? [g().title, g().lead]
-      : [t.heads[S.view], t.lead[S.view](songs.songs.length, rows.length)];
+    const title = S.view === "guide" ? g().title : t.heads[S.view];
     put(head, h("div", { class: "page-head" }, h("div", { class: "page-head-title" }, icon("star", "ic star"), h("h1", {}, title), betaBadge("page-beta-note"),
       h("span", { class: "track", "aria-hidden": "true" })), S.view === "guide" && g().reminder ? h("aside", {id:"page-beta-note",class:"guide-reminder",role:"note"}, h("strong",{},g().reminder.title),g().reminder.priority ? h("p",{},h("strong",{},g().reminder.priority)) : null, h("p",{},modelText(g().reminder.text))) : h("span", {id:"page-beta-note",class:"sr-only"},t.betaNote)));
   };

examples/songs/text.js

@@ -12,10 +12,6 @@ export const UI = {
     jackets: "封面", jacketsHint: "显示或隐藏封面", theme: "切换浅色 / 深色", swap: "交换横纵轴",
     band: "乐队", difficulty: "难度",
     heads: { rank: "谱面排行", charts: "谱面图表" },
-    lead: {
-      rank: (songs, charts) => `${songs} 首歌、${charts} 张谱面的效率、活动评级、速度、等级与时长。得分数值按所选游玩场景计算：默认撃奏ライブ、三个区间都是第 1 名（最佳情况），也可切到不开激走的自由 Live，见说明。点任意一行看谱面详情；作词作曲、音频和谱面预览见 moenotes。`,
-      charts: (songs, charts) => `${songs} 首歌、${charts} 张谱面的分布。散点图的两轴可任选，点任意一点看谱面详情。`,
-    },
     empty: "没有符合条件的谱面", emptyHint: "当前的乐队、难度、搜索词或“只看前沿”把所有谱面都排除了。", clear: "清除筛选",
     diff: { easy: "Easy", normal: "Normal", hard: "Hard", expert: "Expert" },
     rankBy: {
@@ -132,10 +128,6 @@ export const UI = {
     jackets: "Jackets", jacketsHint: "Show or hide the jackets", theme: "Light / dark", swap: "Swap the axes",
     band: "Band", difficulty: "Difficulty",
     heads: { rank: "Chart rankings", charts: "Chart figures" },
-    lead: {
-      rank: (songs, charts) => `Efficiency, event ranks, speed, level and length of ${songs} songs and ${charts} charts. Score figures follow the play scenario chosen: by default Gekisou Live at rank 1 in all three ranges (the best case), or Free Live without Gekisou; see the guide. Open any row for the chart's details; credits, audio and chart previews are on moenotes.`,
-      charts: (songs, charts) => `How ${songs} songs and ${charts} charts spread. Pick any two figures for the scatter; open any point for the chart's details.`,
-    },
     empty: "No chart matches", emptyHint: "The band, difficulties, search or “frontier only” leave out every chart.", clear: "Clear filters",
     diff: { easy: "Easy", normal: "Normal", hard: "Hard", expert: "Expert" },
     rankBy: {
@@ -354,7 +346,6 @@ export const REPLAY_UI = {
 export const GUIDE = {
   "zh": {
     "title": "定义、推导与成立条件",
-    "lead": "排行与适性展示理论最佳打法的统计参考；谱面详情还可逐音符计算给定输入的一局。新 chart-stats/3 使用标称概率期望与计算包围区间，旧 music-data/1 的采样统计仍可读取。两者使用同一套 ournotes-deck Rust 模型，原生逐帧核对的案例见下表。",
     "sections": [
       {
         "title": "得分模型",
@@ -639,7 +630,6 @@ export const GUIDE = {
   },
   "en": {
     "title": "Definitions, derivations and conditions",
-    "lead": "Rankings and aptitude show statistical references for theoretical best play. Chart details can also calculate one play from per-note inputs. New chart-stats/3 data uses nominal expectations and numerical enclosures; legacy music-data/1 samples remain readable. Both use the same ournotes-deck Rust model; the native frame checks are listed below.",
     "sections": [
       {
         "title": "Score model",