Initial

.editorconfig

+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+[src/**.{js,tsx,ts}]
+indent_style = space
+indent_size = 2
+tab_width = 2

.eslintignore

+dist

.eslintrc.js

+module.exports = {
+  env: {
+    browser: true,
+    node: true,
+    es6: true,
+  },
+  extends: [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/eslint-recommended",
+    "plugin:@typescript-eslint/recommended",
+  ],
+  parser: "@typescript-eslint/parser",
+  plugins: ["@typescript-eslint"],
+  globals: {
+    Atomics: "readonly",
+    SharedArrayBuffer: "readonly",
+  },
+  parserOptions: {
+    ecmaVersion: 2018,
+    sourceType: "module",
+  },
+  rules: {
+    "@typescript-eslint/no-var-requires": 0,
+  },
+};

.gitignore

+node_modules
+.idea
+yarn-error.log
+dist

.prettierignore

+dist

README.md

+# MIME Verifier

__tests__/index.test.ts

+import { describe, it, expect } from "@jest/globals";
+import {add} from "../src";
+
+describe("index test", () => {
+  it("should calculate sum", () => {
+    const sum = add(2, 5);
+    expect(sum).toEqual(7);
+  })
+})

babel.config.js

+module.exports = {
+  presets: [
+    [
+      "@babel/preset-env",
+      {
+        targets: {
+          node: "current",
+        },
+      },
+    ],
+    "@babel/preset-typescript",
+  ],
+};

jest.config.js

+// For a detailed explanation regarding each configuration property, visit:
+// https://jestjs.io/docs/en/configuration.html
+
+module.exports = {
+  // All imported modules in your tests should be mocked automatically
+  // automock: false,
+
+  // Stop running tests after `n` failures
+  // bail: 0,
+
+  // The directory where Jest should store its cached dependency information
+  // cacheDirectory: "/private/var/folders/1y/frzcyzpj5s90s0x39psh8_xw0000gn/T/jest_dx",
+
+  // Automatically clear mock calls and instances between every test
+  clearMocks: true,
+
+  // Indicates whether the coverage information should be collected while executing the test
+  // collectCoverage: false,
+
+  // An array of glob patterns indicating a set of files for which coverage information should be collected
+  // collectCoverageFrom: undefined,
+
+  // The directory where Jest should output its coverage files
+  // coverageDirectory: undefined,
+
+  // An array of regexp pattern strings used to skip coverage collection
+  // coveragePathIgnorePatterns: [
+  //   "/node_modules/"
+  // ],
+
+  // Indicates which provider should be used to instrument code for coverage
+  // coverageProvider: "babel",
+
+  // A list of reporter names that Jest uses when writing coverage reports
+  // coverageReporters: [
+  //   "json",
+  //   "text",
+  //   "lcov",
+  //   "clover"
+  // ],
+
+  // An object that configures minimum threshold enforcement for coverage results
+  // coverageThreshold: undefined,
+
+  // A path to a custom dependency extractor
+  // dependencyExtractor: undefined,
+
+  // Make calling deprecated APIs throw helpful error messages
+  // errorOnDeprecated: false,
+
+  // Force coverage collection from ignored files using an array of glob patterns
+  // forceCoverageMatch: [],
+
+  // A path to a module which exports an async function that is triggered once before all test suites
+  // globalSetup: "./__tests__/setupFiles.js",
+
+  // A path to a module which exports an async function that is triggered once after all test suites
+  // globalTeardown: undefined,
+
+  // A set of global variables that need to be available in all test environments
+  // globals: {},
+
+  // The maximum amount of workers used to run your tests. Can be specified as % or a number. E.g. maxWorkers: 10% will use 10% of your CPU amount + 1 as the maximum worker number. maxWorkers: 2 will use a maximum of 2 workers.
+  // maxWorkers: "50%",
+
+  // An array of directory names to be searched recursively up from the requiring module's location
+  // moduleDirectories: [
+  //   "node_modules"
+  // ],
+
+  // An array of file extensions your modules use
+  // moduleFileExtensions: [
+  //   "js",
+  //   "json",
+  //   "jsx",
+  //   "ts",
+  //   "tsx",
+  //   "node"
+  // ],
+
+  // A map from regular expressions to module names or to arrays of module names that allow to stub out resources with a single module
+  // moduleNameMapper: {},
+
+  // An array of regexp pattern strings, matched against all module paths before considered 'visible' to the module loader
+  modulePathIgnorePatterns: ["testData.ts"],
+
+  // Activates notifications for test results
+  // notify: false,
+
+  // An enum that specifies notification mode. Requires { notify: true }
+  // notifyMode: "failure-change",
+
+  // A preset that is used as a base for Jest's configuration
+  // preset: undefined,
+
+  // Run tests from one or more projects
+  // projects: undefined,
+
+  // Use this configuration option to add custom reporters to Jest
+  // reporters: undefined,
+
+  // Automatically reset mock state between every test
+  // resetMocks: false,
+
+  // Reset the module registry before running each individual test
+  // resetModules: false,
+
+  // A path to a custom resolver
+  // resolver: undefined,
+
+  // Automatically restore mock state between every test
+  // restoreMocks: false,
+
+  // The root directory that Jest should scan for tests and modules within
+  // rootDir: undefined,
+
+  // A list of paths to directories that Jest should use to search for files in
+  // roots: [
+  //   "<rootDir>"
+  // ],
+
+  // Allows you to use a custom runner instead of Jest's default test runner
+  // runner: "jest-runner",
+
+  // The paths to modules that run some code to configure or set up the testing environment before each test
+  // setupFiles: ["./__tests__/setupFiles.js"],
+
+  // A list of paths to modules that run some code to configure or set up the testing framework before each test
+  // setupFilesAfterEnv: [],
+
+  // The number of seconds after which a test is considered as slow and reported as such in the results.
+  // slowTestThreshold: 5,
+
+  // A list of paths to snapshot serializer modules Jest should use for snapshot testing
+  // snapshotSerializers: [],
+
+  // The test environment that will be used for testing
+  testEnvironment: "jest-environment-node",
+
+  // Options that will be passed to the testEnvironment
+  // testEnvironmentOptions: {},
+
+  // Adds a location field to test results
+  // testLocationInResults: false,
+
+  // The glob patterns Jest uses to detect test files
+  // testMatch: [
+  //   "**/__tests__/**/*.[jt]s?(x)",
+  //   "**/?(*.)+(spec|test).[tj]s?(x)"
+  // ],
+
+  // An array of regexp pattern strings that are matched against all test paths, matched tests are skipped
+  testPathIgnorePatterns: ["/node_modules/", "setupFiles.js"],
+
+  // The regexp pattern or array of patterns that Jest uses to detect test files
+  // testRegex: [],
+
+  // This option allows the use of a custom results processor
+  // testResultsProcessor: undefined,
+
+  // This option allows use of a custom test runner
+  // testRunner: "jasmine2",
+
+  // This option sets the URL for the jsdom environment. It is reflected in properties such as location.href
+  // testURL: "http://localhost",
+
+  // Setting this value to "fake" allows the use of fake timers for functions such as "setTimeout"
+  // timers: "real",
+
+  // A map from regular expressions to paths to transformers
+  // transform: undefined,
+
+  // An array of regexp pattern strings that are matched against all source file paths, matched files will skip transformation
+  // transformIgnorePatterns: [
+  //   "/node_modules/",
+  //   "\\.pnp\\.[^\\/]+$"
+  // ],
+
+  // An array of regexp pattern strings that are matched against all modules before the module loader will automatically return a mock for them
+  // unmockedModulePathPatterns: undefined,
+
+  // Indicates whether each individual test should be reported during the run
+  // verbose: undefined,
+
+  // An array of regexp patterns that are matched against all source file paths before re-running tests in watch mode
+  // watchPathIgnorePatterns: [],
+
+  // Whether to use watchman for file crawling
+  // watchman: true,
+};

lint-staged.config.js

+module.exports = {
+  "*.+(js|ts)": ["eslint --fix", "git add"],
+  "*.+(js|ts|json|md)": ["prettier --write", "git add"],
+};

package.json

+{
+  "name": "@vereign/mime-verifier",
+  "author": "Igor Markin <igor.markin@vereign.com>",
+  "description": "A library that handles verification of MIME messages",
+  "version": "1.0.0",
+  "license": "MIT",
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "devDependencies": {
+    "@babel/core": "^7.11.4",
+    "@babel/preset-env": "^7.11.0",
+    "@babel/preset-typescript": "^7.10.4",
+    "@typescript-eslint/eslint-plugin": "^3.10.1",
+    "@typescript-eslint/parser": "^3.10.1",
+    "babel-eslint": "^10.1.0",
+    "babel-jest": "^26.3.0",
+    "eslint": "^7.7.0",
+    "husky": "^4.2.5",
+    "jest": "^26.4.2",
+    "lint-staged": "^10.2.13",
+    "prettier": "^2.1.1",
+    "typescript": "^4.0.2"
+  },
+  "scripts": {
+    "prepare": "yarn build",
+    "start": "tsc --watch",
+    "build": "tsc",
+    "test": "jest",
+    "test:watch": "jest --watch",
+    "eslint": "eslint src/"
+  },
+  "husky": {
+    "hooks": {
+      "pre-commit": "lint-staged"
+    }
+  },
+  "dependencies": {}
+}

src/index.ts

+export const add = (a: number, b: number) => {
+  return a + b;
+}

tsconfig.json

+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "target": "es2015",
+    "declaration": true,
+    "outDir": "./dist",
+    "allowJs": true
+  },
+  "include": ["src/**/*"]
+}