Bump deps to latest major version and other misc dev UX

.prettierrc.js

@@ -1,4 +1,16 @@
-module.exports = {
+/** @type {import('prettier').Config} */
+const config = {
   trailingComma: 'none',
-  singleQuote: true
+  singleQuote: true,
+  endOfLine: 'auto',
+  overrides: [
+    {
+      files: ['tsconfig.json', 'jsconfig.json', 'tsconfig.*.json'],
+      options: {
+        parser: 'jsonc'
+      }
+    }
+  ]
 };
+
+export default config;

.vscode/extensions.json

@@ -2,7 +2,6 @@
   "recommendations": [
     "editorconfig.editorconfig",
     "esbenp.prettier-vscode",
-    "dbaeumer.vscode-eslint",
-    "eg2.vscode-npm-script"
+    "dbaeumer.vscode-eslint"
   ]
 }

.vscode/settings.json

@@ -2,5 +2,7 @@
   "javascript.preferences.quoteStyle": "single",
   "prettier.requireConfig": true,
   "prettier.useEditorConfig": true,
-  "editor.formatOnSave": true
+  "editor.formatOnSave": true,
+  "prettier.ignorePath": ".prettierignore",
+  "typescript.tsdk": "node_modules\\typescript\\lib"
 }

babel.config.js

@@ -1,23 +1,40 @@
-module.exports = (api) => {
-  api.cache.never();
+import Module from 'node:module';
+
+const require = Module.createRequire(import.meta.url);
+
+// From: https://github.com/babel/babel-polyfills/blob/a5db9c31c5b5474b4018e6178bc40882fc3eb5bf/packages/babel-plugin-polyfill-corejs3/README.md#version
+
+const {
+  version: babelruntimeVersion
+} = require('@babel/runtime-corejs3/package.json');
+const { version: corejspureVersion } = require('core-js-pure/package.json');
+
+/** @type {import('@babel/core').ConfigFunction} */
+function makeConfig(api) {
+  api.cache.invalidate(() => babelruntimeVersion + corejspureVersion);
 
   return {
     // Fixes "TypeError: __webpack_require__(...) is not a function"
     // https://github.com/webpack/webpack/issues/9379#issuecomment-509628205
-    // https://babeljs.io/docs/en/options#sourcetype
+    // https://babel.dev/docs/options#sourcetype
     sourceType: 'unambiguous',
+    // https://babel.dev/docs/assumptions
+    assumptions: {
+      noNewArrows: true
+    },
     plugins: [
       [
         '@babel/plugin-transform-runtime',
         {
           regenerator: false,
-          version: require('./package.json').dependencies['@babel/runtime']
+          version: babelruntimeVersion
         }
       ],
       [
         'polyfill-corejs3',
         {
-          method: 'usage-pure'
+          method: 'usage-pure',
+          version: corejspureVersion
         }
       ],
       [
@@ -36,4 +53,6 @@ module.exports = (api) => {
       ]
     ]
   };
-};
+}
+
+export default makeConfig;

eslint.config.js

@@ -0,0 +1,101 @@
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import Module from 'node:module';
+
+import eslintJs from '@eslint/js';
+import prettierConfig from 'eslint-config-prettier';
+// @ts-expect-error No type definitions available for this package. https://github.com/ota-meshi/eslint-plugin-regexp/issues/723
+import * as regexpPlugin from 'eslint-plugin-regexp';
+import globals from 'globals';
+
+const require = Module.createRequire(import.meta.url);
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+/** @type {'module' | 'commonjs'} */
+const defaultSourceType =
+  require(join(__dirname, 'package.json')).type ?? 'commonjs';
+
+/** @type {import('eslint').Linter.FlatConfig[]} */
+export default [
+  eslintJs.configs.recommended,
+  prettierConfig,
+  regexpPlugin.configs['flat/recommended'],
+
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error'
+    },
+
+    languageOptions: {
+      sourceType: defaultSourceType,
+      parserOptions: {
+        ecmaFeatures: {
+          impliedStrict: true
+        }
+      },
+      globals: {
+        ...globals.nodeBuiltin
+      }
+    },
+
+    rules: {
+      'no-var': 'error',
+      'no-await-in-loop': 'error',
+      'no-implicit-globals': ['error'],
+      'no-unused-vars': ['error', { vars: 'local', argsIgnorePattern: '^_' }],
+      'no-useless-rename': ['error'],
+      'arrow-body-style': ['error', 'as-needed'],
+      'no-lonely-if': 'error',
+      'prefer-object-has-own': 'error',
+      'prefer-exponentiation-operator': 'error',
+      'prefer-regex-literals': ['error', { disallowRedundantWrapping: true }],
+      'array-callback-return': [
+        'error',
+        { checkForEach: true, allowVoid: true }
+      ],
+      'no-constructor-return': 'error',
+      'no-unmodified-loop-condition': 'error',
+      'no-useless-assignment': 'error',
+
+      /* eslint-plugin-regexp */
+      'regexp/prefer-character-class': ['error', { minAlternatives: 2 }],
+      'regexp/no-empty-alternative': 'error', // Set to warn in recommended config
+      'regexp/no-lazy-ends': 'error', // Set to warn in recommended config
+      'regexp/no-potentially-useless-backreference': 'error', // Set to warn in recommended config
+      'regexp/confusing-quantifier': 'error', // Set to warn in recommended config
+      'regexp/no-useless-flag': 'error', // Set to warn in recommended config
+      'regexp/optimal-lookaround-quantifier': 'error' // Set to warn in recommended config
+    }
+  },
+
+  {
+    files: ['src/**/*'],
+    languageOptions: {
+      globals: {
+        ...globals.browser
+      }
+    }
+  },
+
+  {
+    // Why doesn't ESLint do this by default is beyond me.
+    files: ['**/*.cjs'],
+    languageOptions: {
+      sourceType: 'commonjs'
+    }
+  },
+
+  {
+    // Why doesn't ESLint do this by default is beyond me.
+    files: ['**/*.mjs'],
+    languageOptions: {
+      sourceType: 'module'
+    }
+  },
+
+  {
+    // `ignores` field must be in the very bottom config.
+    ignores: ['dist/**/*', '**/*-polyfill.*']
+  }
+];

lint-staged.config.js

@@ -0,0 +1,10 @@
+function globForCode(/** @type {string} */ toolName) {
+  return '*.?(c|m){js,ts}?(x)' + `*(${toolName})`;
+}
+
+/** @type {import('lint-staged').Config} */
+export default {
+  '*': 'prettier --ignore-unknown --write',
+  [globForCode('eslint')]: 'eslint',
+  [globForCode('tsc')]: () => 'tsc -b'
+};