Update dependencies and require Node.js 10

.travis.yml

@@ -2,4 +2,3 @@ language: node_js
 node_js:
   - '12'
   - '10'
-  - '8'

index.d.ts

@@ -1,9 +1,9 @@
 declare namespace mem {
 	interface CacheStorage<KeyType, ValueType> {
-		has(key: KeyType): boolean;
-		get(key: KeyType): ValueType | undefined;
-		set(key: KeyType, value: ValueType): void;
-		delete(key: KeyType): void;
+		has: (key: KeyType) => boolean;
+		get: (key: KeyType) => ValueType | undefined;
+		set: (key: KeyType, value: ValueType) => void;
+		delete: (key: KeyType) => void;
 		clear?: () => void;
 	}
 
@@ -100,9 +100,9 @@ declare const mem: {
 
 	@param fn - Memoized function.
 	*/
-	clear<ArgumentsType extends unknown[], ReturnType>(
+	clear: <ArgumentsType extends unknown[], ReturnType>(
 		fn: (...arguments: ArgumentsType) => ReturnType
-	): void;
+	) => void;
 };
 
 export = mem;

index.js

@@ -35,7 +35,7 @@ const mem = (fn, {
 		// The below call will throw in some host environments
 		// See https://github.com/sindresorhus/mimic-fn/issues/10
 		mimicFn(memoized, fn);
-	} catch (_) {}
+	} catch {}
 
 	cacheStore.set(memoized, cache);
 

package.json

@@ -11,7 +11,7 @@
 		"url": "https://sindresorhus.com"
 	},
 	"engines": {
-		"node": ">=8"
+		"node": ">=10"
 	},
 	"scripts": {
 		"test": "xo && ava && tsd"
@@ -38,10 +38,16 @@
 		"mimic-fn": "^3.0.0"
 	},
 	"devDependencies": {
-		"ava": "^2.4.0",
+		"@types/serialize-javascript": "^4.0.0",
+		"ava": "^3.13.0",
 		"delay": "^4.1.0",
-		"serialize-javascript": "^2.1.0",
-		"tsd": "^0.11.0",
-		"xo": "^0.25.3"
+		"serialize-javascript": "^5.0.1",
+		"tsd": "^0.13.1",
+		"xo": "^0.33.1"
+	},
+	"xo": {
+		"rules": {
+			"@typescript-eslint/member-ordering": "off"
+		}
 	}
 }

test-d/index.test-d.ts

@@ -0,0 +1,32 @@
+import {expectType} from 'tsd';
+import mem = require('..');
+
+const fn = (text: string) => Boolean(text);
+
+expectType<typeof fn>(mem(fn));
+expectType<typeof fn>(mem(fn, {maxAge: 1}));
+expectType<typeof fn>(mem(fn, {cacheKey: ([firstArgument]) => firstArgument}));
+expectType<typeof fn>(
+	mem(fn, {
+		// The cacheKey returns an array. This isn't deduplicated by a regular Map, but it's valid. The correct solution would be to use ManyKeysMap to deduplicate it correctly
+		cacheKey: (arguments_: [string]) => arguments_,
+		cache: new Map<[string], {data: boolean; maxAge: number}>()
+	})
+);
+expectType<typeof fn>(
+	// The `firstArgument` of `fn` is of type `string`, so it's used
+	mem(fn, {cache: new Map<string, {data: boolean; maxAge: number}>()})
+);
+
+/* Overloaded function tests */
+function overloadedFn(parameter: false): false;
+function overloadedFn(parameter: true): true;
+function overloadedFn(parameter: boolean): boolean {
+	return parameter;
+}
+
+expectType<typeof overloadedFn>(mem(overloadedFn));
+expectType<true>(mem(overloadedFn)(true));
+expectType<false>(mem(overloadedFn)(false));
+
+mem.clear(fn);

test.js

@@ -1,7 +1,7 @@
-import test from 'ava';
-import delay from 'delay';
-import serializeJavascript from 'serialize-javascript';
-import mem from '.';
+const test = require('ava');
+const delay = require('delay');
+const serializeJavascript = require('serialize-javascript');
+const mem = require('.');
 
 test('memoize', t => {
 	let i = 0;
@@ -132,7 +132,9 @@ test('maxAge items are deleted even if function throws', async t => {
 	await delay(50);
 	t.is(memoized(1), 0);
 	await delay(200);
-	t.throws(() => memoized(1), 'failure');
+	t.throws(() => memoized(1), {
+		message: 'failure'
+	});
 	t.is(cache.size, 0);
 });
 
@@ -195,5 +197,7 @@ test('prototype support', t => {
 test('mem.clear() throws when called with a plain function', t => {
 	t.throws(() => {
 		mem.clear(() => {});
-	}, 'Can\'t clear a function that was not memoized!');
+	}, {
+		message: 'Can\'t clear a function that was not memoized!'
+	});
 });