Require Node.js 8, add TypeScript definition (#2)

.editorconfig

@@ -7,6 +7,6 @@ charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
 
-[{package.json,*.yml}]
+[*.yml]
 indent_style = space
 indent_size = 2

.gitattributes

@@ -1,2 +1 @@
-* text=auto
-*.js text eol=lf
+* text=auto eol=lf

.gitignore

@@ -1 +1,2 @@
 node_modules
+yarn.lock

.npmrc

@@ -0,0 +1 @@
+package-lock=false

.travis.yml

@@ -1,4 +1,4 @@
 language: node_js
 node_js:
-  - '6'
-  - '4'
+  - '10'
+  - '8'

index.d.ts

@@ -0,0 +1,6 @@
+/**
+ * Check if a value is an error constructor.
+ */
+export default function isErrorConstructor(
+	value: unknown
+): value is ErrorConstructor;

index.js

@@ -1,2 +1,7 @@
 'use strict';
-module.exports = ctor => (ctor === Error || ctor.prototype instanceof Error);
+
+const isErrorConstructor = constructor =>
+	constructor === Error || constructor.prototype instanceof Error;
+
+module.exports = isErrorConstructor;
+module.exports.default = isErrorConstructor;

index.test-d.ts

@@ -0,0 +1,8 @@
+import {expectType} from 'tsd-check';
+import isErrorConstructor from '.';
+
+const foo = 'foo';
+
+if (isErrorConstructor(foo)) {
+	expectType<ErrorConstructor>(foo);
+}

package.json

@@ -1,38 +1,37 @@
 {
-  "name": "is-error-constructor",
-  "version": "1.0.1",
-  "description": "Check if a value is an error constructor",
-  "license": "MIT",
-  "repository": "sindresorhus/is-error-constructor",
-  "author": {
-    "name": "Sindre Sorhus",
-    "email": "sindresorhus@gmail.com",
-    "url": "sindresorhus.com"
-  },
-  "engines": {
-    "node": ">=4"
-  },
-  "scripts": {
-    "test": "xo && ava"
-  },
-  "files": [
-    "index.js"
-  ],
-  "keywords": [
-    "is",
-    "error",
-    "constructor",
-    "err",
-    "ctor",
-    "check",
-    "detect",
-    "instanceof"
-  ],
-  "devDependencies": {
-    "ava": "*",
-    "xo": "*"
-  },
-  "xo": {
-    "esnext": true
-  }
+	"name": "is-error-constructor",
+	"version": "1.0.1",
+	"description": "Check if a value is an error constructor",
+	"license": "MIT",
+	"repository": "sindresorhus/is-error-constructor",
+	"author": {
+		"name": "Sindre Sorhus",
+		"email": "sindresorhus@gmail.com",
+		"url": "sindresorhus.com"
+	},
+	"engines": {
+		"node": ">=8"
+	},
+	"scripts": {
+		"test": "xo && ava && tsd-check"
+	},
+	"files": [
+		"index.js",
+		"index.d.ts"
+	],
+	"keywords": [
+		"is",
+		"error",
+		"constructor",
+		"err",
+		"ctor",
+		"check",
+		"detect",
+		"instanceof"
+	],
+	"devDependencies": {
+		"ava": "^1.3.1",
+		"tsd-check": "^0.3.0",
+		"xo": "^0.24.0"
+	}
 }

test.js

@@ -1,6 +1,6 @@
 import assert from 'assert';
 import test from 'ava';
-import m from './';
+import isErrorConstructor from '.';
 
 class CustomError extends RangeError {
 	constructor() {
@@ -9,20 +9,20 @@ class CustomError extends RangeError {
 	}
 }
 
-test(t => {
-	t.true(m(Error));
-	t.true(m(RangeError));
-	t.true(m(SyntaxError));
-	t.true(m(assert.AssertionError));
-	t.true(m(CustomError));
-	t.false(m(() => {}));
-	t.false(m({}));
-	t.false(m(''));
-	t.false(m(new Error()));
-	t.false(m(new assert.AssertionError({
+test('isErrorConstructor', t => {
+	t.true(isErrorConstructor(Error));
+	t.true(isErrorConstructor(RangeError));
+	t.true(isErrorConstructor(SyntaxError));
+	t.true(isErrorConstructor(assert.AssertionError));
+	t.true(isErrorConstructor(CustomError));
+	t.false(isErrorConstructor(() => {}));
+	t.false(isErrorConstructor({}));
+	t.false(isErrorConstructor(''));
+	t.false(isErrorConstructor(new Error()));
+	t.false(isErrorConstructor(new assert.AssertionError({
 		actual: '',
 		expected: '',
 		operator: ''
 	})));
-	t.false(m(new CustomError()));
+	t.false(isErrorConstructor(new CustomError()));
 });