Set up linting.

.eslintrc

@@ -0,0 +1,185 @@
+{
+  env: {
+    node: true,
+    es2021: true,
+  },
+
+  parserOptions: {
+    sourceType: "module",
+  },
+
+  rules: {
+    // Possible Errors
+    comma-dangle: [2, "always-multiline"],
+    no-cond-assign: 0,
+    no-console: [2, { allow: ["error"] }],
+    no-constant-condition: 0,
+    no-debugger: 2,
+    no-dupe-args: 2,
+    no-dupe-keys: 2,
+    no-duplicate-case: 2,
+    no-empty: 2,
+    no-empty-character-class: 2,
+    no-ex-assign: 2,
+    no-extra-boolean-cast: 2,
+    no-extra-parens: 0,
+    no-extra-semi: 2,
+    no-func-assign: 2,
+    no-inner-declarations: 2,
+    no-invalid-regexp: 2,
+    no-irregular-whitespace: 2,
+    no-negated-in-lhs: 2,
+    no-obj-calls: 2,
+    no-regex-spaces: 2,
+    no-sparse-arrays: 2,
+    no-unreachable: 2,
+    use-isnan: 2,
+    valid-jsdoc: 0,
+    valid-typeof: 2,
+    no-unexpected-multiline: 2,
+
+    // Best Practices
+    accessor-pairs: 2,
+    block-scoped-var: 2,
+    complexity: 0,
+    consistent-return: 0,
+    curly: 0,
+    default-case: 0,
+    dot-notation: 2,
+    dot-location: [2, "property"],
+    eqeqeq: 2,
+    guard-for-in: 0,
+    no-alert: 2,
+    no-caller: 2,
+    no-div-regex: 2,
+    no-else-return: 0,
+    no-labels: 2,
+    no-eq-null: 2,
+    no-eval: 2,
+    no-extend-native: 2,
+    no-extra-bind: 2,
+    no-fallthrough: 0,
+    no-floating-decimal: 2,
+    no-implicit-coercion: 0,
+    no-implied-eval: 2,
+    no-invalid-this: 2,
+    no-iterator: 2,
+    no-lone-blocks: 2,
+    no-loop-func: 2,
+    no-multi-spaces: 0,
+    no-multi-str: 2,
+    no-native-reassign: 2,
+    no-new-func: 2,
+    no-new-wrappers: 2,
+    no-new: 2,
+    no-octal-escape: 2,
+    no-octal: 2,
+    no-param-reassign: 0,
+    no-process-env: 2,
+    no-proto: 2,
+    no-redeclare: 2,
+    no-return-assign: 0,
+    no-script-url: 2,
+    no-self-compare: 2,
+    no-sequences: 0, // allow the comma operator
+    no-throw-literal: 2,
+    no-unused-expressions: 0,
+    no-useless-call: 2,
+    no-void: 2,
+    no-warning-comments: 2,
+    no-with: 2,
+    radix: 2,
+    vars-on-top: 0,
+    wrap-iife: [2, "inside"],
+    yoda: 2,
+
+    // Strict Mode
+    strict: [2, "never"],
+
+    // Variables
+    init-declarations: 0,
+    no-catch-shadow: 2,
+    no-delete-var: 2,
+    no-label-var: 2,
+    no-shadow-restricted-names: 2,
+    no-shadow: 0,
+    no-undef-init: 2,
+    no-undef: 2,
+    no-undefined: 0,
+    no-unused-vars: [ 2, { args: "none" }],
+    no-use-before-define: [2, { functions: false, classes: false }],
+
+    // Node.js
+    callback-return: 2,
+    handle-callback-err: 2,
+    no-mixed-requires: 2,
+    no-new-require: 2,
+    no-path-concat: 2,
+    no-process-exit: 0,
+    no-restricted-modules: 2,
+    no-sync: 2,
+
+    // Stylistic Issues
+    array-bracket-spacing: 2,
+    arrow-parens: [2, "as-needed"],
+    block-spacing: 2,
+    brace-style: [2, "stroustrup", { allowSingleLine: true }],
+    camelcase: 2,
+    comma-spacing: 2,
+    comma-style: 2,
+    computed-property-spacing: 2,
+    consistent-this: 0,
+    eol-last: 2,
+    func-names: 0,
+    func-style: [2, "declaration"],
+    id-length: 0,
+    id-match: 2,
+    indent-legacy: [2, 2, { VariableDeclarator: 2 }],
+    key-spacing: [2, { mode: "minimum" }],
+    lines-around-comment: 2,
+    linebreak-style: 2,
+    max-nested-callbacks: [2, 1],
+    new-cap: 2,
+    new-parens: 2,
+    newline-after-var: 0,
+    no-array-constructor: 2,
+    no-const-assign: 2,
+    no-continue: 2,
+    no-inline-comments: 0,
+    no-lonely-if: 2,
+    no-mixed-spaces-and-tabs: 2,
+    no-multiple-empty-lines: 0,
+    no-nested-ternary: 0,
+    no-new-object: 2,
+    no-spaced-func: 2,
+    no-ternary: 0,
+    no-trailing-spaces: 2,
+    no-underscore-dangle: 0,
+    no-unneeded-ternary: 2,
+    no-var: 2,
+    object-curly-spacing: [2, "always"],
+    object-curly-newline: 0,
+    object-property-newline: 0,
+    one-var: 0,
+    operator-assignment: 2,
+    operator-linebreak: [2, "after", { overrides: { ":": "ignore" } }],
+    padded-blocks: [2, "never"],
+    prefer-arrow-callback: 2,
+    prefer-const: 2,
+    prefer-template: 2,
+    quote-props: [2, "consistent-as-needed"],
+    quotes: [2, "single", "avoid-escape"],
+    semi-spacing: 2,
+    semi: 2,
+    sort-vars: 0,
+    keyword-spacing: 2,
+    space-before-blocks: 2,
+    space-before-function-paren: [2, {"anonymous": "always", "named": "never"}],
+    space-in-parens: 2,
+    space-infix-ops: 2,
+    space-unary-ops: 2,
+    spaced-comment: [2, "always", { block: { markers: ["!"] } }],
+    template-curly-spacing: 2,
+    wrap-regex: 0,
+  },
+}

.husky/pre-commit

@@ -0,0 +1,4 @@
+#!/usr/bin/env sh
+. "$(dirname -- "$0")/_/husky.sh"
+
+npm run lint