[New] add types

.editorconfig

@@ -0,0 +1,20 @@
+root = true
+
+[*]
+indent_style = tab
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+max_line_length = 150
+
+[CHANGELOG.md]
+indent_style = space
+indent_size = 2
+
+[*.json]
+max_line_length = off
+
+[Makefile]
+max_line_length = off

index.d.ts

@@ -0,0 +1,11 @@
+type primitive = string | number | bigint | boolean | symbol | null | undefined;
+
+declare function whichBoxedPrimitive(value: primitive): null;
+declare function whichBoxedPrimitive(value: BigInt): 'BigInt';
+declare function whichBoxedPrimitive(value: Boolean): 'Boolean';
+declare function whichBoxedPrimitive(value: Number): 'Number';
+declare function whichBoxedPrimitive(value: String): 'String';
+declare function whichBoxedPrimitive(value: Symbol): 'Symbol';
+declare function whichBoxedPrimitive(value: unknown): undefined;
+
+export = whichBoxedPrimitive;

index.js

@@ -6,6 +6,7 @@ var isBoolean = require('is-boolean-object');
 var isSymbol = require('is-symbol');
 var isBigInt = require('is-bigint');
 
+/** @type {import('.')} */
 // eslint-disable-next-line consistent-return
 module.exports = function whichBoxedPrimitive(value) {
 	// eslint-disable-next-line eqeqeq

package.json

@@ -8,6 +8,7 @@
 		"prepublishOnly": "safe-publish-latest",
 		"prepublish": "not-in-publish || npm run prepublishOnly",
 		"lint": "eslint --ext=js,mjs .",
+		"postlint": "tsc -p . && attw -P",
 		"pretest": "npm run lint",
 		"tests-only": "nyc tape 'test/**/*.js'",
 		"test": "npm run tests-only",
@@ -44,7 +45,12 @@
 		"is-symbol": "^1.1.0"
 	},
 	"devDependencies": {
+		"@arethetypeswrong/cli": "^0.17.0",
 		"@ljharb/eslint-config": "^21.1.1",
+		"@ljharb/tsconfig": "^0.2.0",
+		"@types/for-each": "^0.3.3",
+		"@types/object-inspect": "^1.13.0",
+		"@types/tape": "^5.6.5",
 		"auto-changelog": "^2.5.0",
 		"encoding": "^0.1.13",
 		"es-value-fixtures": "^1.5.0",
@@ -55,7 +61,8 @@
 		"nyc": "^10.3.2",
 		"object-inspect": "^1.13.3",
 		"safe-publish-latest": "^2.0.0",
-		"tape": "^5.9.0"
+		"tape": "^5.9.0",
+		"typescript": "next"
 	},
 	"auto-changelog": {
 		"output": "CHANGELOG.md",

tsconfig.json

@@ -0,0 +1,9 @@
+{
+	"extends": "@ljharb/tsconfig",
+	"compilerOptions": {
+		"target": "ES2021",
+	},
+	"exclude": [
+		"coverage"
+	]
+}