add types

index.d.ts

@@ -0,0 +1,3 @@
+declare function isNegativeZero(number: unknown): number is -0;
+
+export = isNegativeZero;

index.js

@@ -1,5 +1,6 @@
 'use strict';
 
+/** @type {import('.')} */
 module.exports = function isNegativeZero(number) {
 	return number === 0 && (1 / number) === -Infinity;
 };

package.json

@@ -8,6 +8,7 @@
 	},
 	"license": "MIT",
 	"main": "index.js",
+	"types": "./index.d.ts",
 	"scripts": {
 		"prepack": "npmignore --auto --commentLines=autogenerated",
 		"prepublishOnly": "safe-publish-latest",
@@ -17,6 +18,7 @@
 		"tests-only": "nyc tape 'test/**/*.js'",
 		"posttest": "aud --production",
 		"lint": "eslint --ext=js,mjs .",
+		"postlint": "tsc -p .",
 		"version": "auto-changelog && git add CHANGELOG.md",
 		"postversion": "auto-changelog && git add CHANGELOG.md && git commit --no-edit --amend && git tag -f \"v$(node -e \"console.log(require('./package.json').version)\")\""
 	},
@@ -40,14 +42,16 @@
 	],
 	"devDependencies": {
 		"@ljharb/eslint-config": "^21.1.0",
+		"@types/tape": "^5.6.4",
 		"aud": "^2.0.4",
 		"auto-changelog": "^2.4.0",
 		"eslint": "=8.8.0",
 		"in-publish": "^2.0.1",
 		"npmignore": "^0.3.1",
 		"nyc": "^10.3.2",
 		"safe-publish-latest": "^2.0.0",
-		"tape": "^5.7.5"
+		"tape": "^5.7.5",
+		"typescript": "next"
 	},
 	"testling": {
 		"files": "test/index.js",

test/index.js

@@ -4,6 +4,7 @@ var test = require('tape');
 var isNegativeZero = require('../');
 
 test('not negative zero', function (t) {
+	// @ts-expect-error
 	t.notOk(isNegativeZero(), 'undefined is not negative zero');
 	t.notOk(isNegativeZero(null), 'null is not negative zero');
 	t.notOk(isNegativeZero(false), 'false is not negative zero');

tsconfig.json

@@ -0,0 +1,49 @@
+{
+  "compilerOptions": {
+    /* Visit https://aka.ms/tsconfig to read more about this file */
+
+    /* Projects */
+
+    /* Language and Environment */
+    "target": "ESNext",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
+    // "lib": [],                                        /* Specify a set of bundled library declaration files that describe the target runtime environment. */
+    // "noLib": true,                                    /* Disable including any library files, including the default lib.d.ts. */
+    "useDefineForClassFields": true,                     /* Emit ECMAScript-standard-compliant class fields. */
+    // "moduleDetection": "auto",                        /* Control what method is used to detect module-format JS files. */
+
+    /* Modules */
+    "module": "commonjs",                                /* Specify what module code is generated. */
+    // "rootDir": "./",                                  /* Specify the root folder within your source files. */
+    // "moduleResolution": "node10",                     /* Specify how TypeScript looks up a file from a given module specifier. */
+    // "baseUrl": "./",                                  /* Specify the base directory to resolve non-relative module names. */
+    // "paths": {},                                      /* Specify a set of entries that re-map imports to additional lookup locations. */
+    // "rootDirs": [],                                   /* Allow multiple folders to be treated as one when resolving modules. */
+    "typeRoots": ["types"],                              /* Specify multiple folders that act like './node_modules/@types'. */
+    "resolveJsonModule": true,                           /* Enable importing .json files. */
+    // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
+
+    /* JavaScript Support */
+    "allowJs": true,                                     /* Allow JavaScript files to be a part of your program. Use the 'checkJS' option to get errors from these files. */
+    "checkJs": true,                                     /* Enable error reporting in type-checked JavaScript files. */
+    "maxNodeModuleJsDepth": 0,                           /* Specify the maximum folder depth used for checking JavaScript files from 'node_modules'. Only applicable with 'allowJs'. */
+
+    /* Emit */
+    "declaration": true,                                 /* Generate .d.ts files from TypeScript and JavaScript files in your project. */
+    "declarationMap": true,                              /* Create sourcemaps for d.ts files. */
+    "noEmit": true,                                      /* Disable emitting files from a compilation. */
+
+    /* Interop Constraints */
+    "allowSyntheticDefaultImports": true,                /* Allow 'import x from y' when a module doesn't have a default export. */
+    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
+    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */
+
+    /* Type Checking */
+    "strict": true,                                      /* Enable all strict type-checking options. */
+
+    /* Completeness */
+    //"skipLibCheck": true                                 /* Skip type checking all .d.ts files. */
+  },
+  "exclude": [
+    "coverage"
+  ]
+}