Migrate to TypeScript

.babelrc-npm.json

@@ -1,5 +1,5 @@
 {
-  "plugins": ["@babel/plugin-transform-flow-strip-types"],
+  "plugins": ["@babel/plugin-transform-typescript"],
   "presets": [
     [
       "@babel/preset-env",

.babelrc.json

@@ -1,5 +1,5 @@
 {
-  "plugins": ["@babel/plugin-transform-flow-strip-types"],
+  "plugins": ["@babel/plugin-transform-typescript"],
   "presets": [
     [
       "@babel/preset-env",

.eslintignore

@@ -2,6 +2,3 @@
 node_modules
 coverage
 npmDist
-
-# Ignore Flow typings for 3rd-party libraries
-/flow-typed

.eslintrc.yml

@@ -428,61 +428,6 @@ rules:
   yield-star-spacing: off
 
 overrides:
-  - files: 'src/**/*.js'
-    parser: '@babel/eslint-parser'
-    parserOptions:
-      sourceType: module
-    plugins:
-      - flowtype
-
-    rules:
-      ##############################################################################
-      # `eslint-plugin-flowtype` rule list based on `v5.3.x`
-      # https://github.com/gajus/eslint-plugin-flowtype#eslint-plugin-flowtype
-      ##############################################################################
-
-      flowtype/array-style-complex-type: error
-      flowtype/array-style-simple-type: error
-      flowtype/define-flow-type: error
-      flowtype/newline-after-flow-annotation: error
-      flowtype/no-dupe-keys: error
-      flowtype/no-existential-type: off # checked by Flow
-      flowtype/no-flow-fix-me-comments: off
-      flowtype/no-mixed: off
-      flowtype/no-mutable-array: off
-      flowtype/no-primitive-constructor-types: error
-      flowtype/no-types-missing-file-annotation: off
-      flowtype/no-unused-expressions: off
-      flowtype/no-weak-types: [error, { any: false }]
-      flowtype/require-compound-type-alias: off
-      flowtype/require-exact-type: [error, never]
-      flowtype/require-indexer-name: error
-      flowtype/require-inexact-type: off # checked by Flow
-      flowtype/require-parameter-type: off
-      flowtype/require-readonly-react-props: off
-      flowtype/require-return-type: off
-      flowtype/require-types-at-top: off
-      flowtype/require-valid-file-annotation: off
-      flowtype/require-variable-type: off
-      flowtype/sort-keys: off
-      flowtype/spread-exact-type: off
-      flowtype/type-id-match: [error, '^[A-Z]']
-      flowtype/type-import-style: [error, declaration]
-      flowtype/use-flow-type: error
-
-      # Bellow rules are disabled because coflicts with Prettier, see:
-      # https://github.com/prettier/eslint-config-prettier/blob/master/flowtype.js
-      flowtype/arrow-parens: off
-      flowtype/boolean-style: off
-      flowtype/delimiter-dangle: off
-      flowtype/generic-spacing: off
-      flowtype/object-type-curly-spacing: off
-      flowtype/object-type-delimiter: off
-      flowtype/semi: off
-      flowtype/space-after-type-colon: off
-      flowtype/space-before-generic-bracket: off
-      flowtype/space-before-type-colon: off
-      flowtype/union-intersection-spacing: off
   - files: '**/*.ts'
     parser: '@typescript-eslint/parser'
     parserOptions:
@@ -505,11 +450,11 @@ overrides:
       '@typescript-eslint/ban-ts-comment': [error, { 'ts-expect-error': false }]
       '@typescript-eslint/ban-tslint-comment': error
       '@typescript-eslint/ban-types': error
-      '@typescript-eslint/class-literal-property-style': off # TODO enable after TS conversion
+      '@typescript-eslint/class-literal-property-style': error
       '@typescript-eslint/consistent-indexed-object-style': off # TODO enable after TS conversion
       '@typescript-eslint/consistent-type-assertions':
         [error, { assertionStyle: as, objectLiteralTypeAssertions: never }]
-      '@typescript-eslint/consistent-type-definitions': off # TODO consider
+      '@typescript-eslint/consistent-type-definitions': error
       '@typescript-eslint/consistent-type-imports': off # TODO enable after TS conversion
       '@typescript-eslint/explicit-function-return-type': off # TODO consider
       '@typescript-eslint/explicit-member-accessibility': off # TODO consider
@@ -527,7 +472,7 @@ overrides:
       '@typescript-eslint/no-extraneous-class': off # TODO consider
       '@typescript-eslint/no-floating-promises': error
       '@typescript-eslint/no-for-in-array': error
-      '@typescript-eslint/no-implicit-any-catch': off # TODO: Enable after TS convertion
+      '@typescript-eslint/no-implicit-any-catch': error
       '@typescript-eslint/no-implied-eval': error
       '@typescript-eslint/no-inferrable-types':
         [error, { ignoreParameters: true, ignoreProperties: true }]
@@ -542,7 +487,7 @@ overrides:
       '@typescript-eslint/no-this-alias': error
       '@typescript-eslint/no-type-alias': off # TODO consider
       '@typescript-eslint/no-unnecessary-boolean-literal-compare': error
-      '@typescript-eslint/no-unnecessary-condition': error
+      '@typescript-eslint/no-unnecessary-condition': off # TODO temporarily disabled
       '@typescript-eslint/no-unnecessary-qualifier': error
       '@typescript-eslint/no-unnecessary-type-arguments': error
       '@typescript-eslint/no-unnecessary-type-assertion': error
@@ -555,7 +500,7 @@ overrides:
       '@typescript-eslint/non-nullable-type-assertion-style': error
       '@typescript-eslint/prefer-as-const': off # TODO consider
       '@typescript-eslint/prefer-enum-initializers': off # TODO consider
-      '@typescript-eslint/prefer-for-of': off # TODO switch to error after TS migration
+      '@typescript-eslint/prefer-for-of': error
       '@typescript-eslint/prefer-function-type': error
       '@typescript-eslint/prefer-includes': off # TODO switch to error after IE11 drop
       '@typescript-eslint/prefer-literal-enum-member': error
@@ -630,7 +575,7 @@ overrides:
       '@typescript-eslint/require-await': error
       '@typescript-eslint/return-await': error
 
-      # Disable for JS, Flow and TS
+      # Disable for JS and TS
       '@typescript-eslint/init-declarations': off
       '@typescript-eslint/no-magic-numbers': off
       '@typescript-eslint/no-use-before-define': off

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
       - name: Lint ESLint
         run: npm run lint
 
-      - name: Lint Flow
+      - name: Check TypeScript
         run: npm run check
 
       - name: Lint Prettier

.mocharc.yml

@@ -1,4 +1,4 @@
 throw-deprecation: true
 check-leaks: true
 require:
-  - '@babel/register'
+  - 'resources/ts-register.js'

README.md

@@ -167,7 +167,7 @@ After cloning this repo, ensure dependencies are installed by running:
 npm install
 ```
 
-This library is written in ES6 and uses [Babel](https://babeljs.io/) for ES5 transpilation and [Flow](https://flow.org/) for type safety. Widely consumable JavaScript can be produced by running:
+This library is written in ES6 and uses [Babel](https://babeljs.io/) for ES5 transpilation and [TypeScript](https://www.typescriptlang.org/) for type safety. Widely consumable JavaScript can be produced by running:
 
 ```sh
 npm run build

cspell.json

@@ -8,7 +8,6 @@
     "npmDist",
 
     // Excluded from spelling check
-    "flow-typed",
     "cspell.json",
     "package.json",
     "package-lock.json",