diff --git a/src/cardinals.js b/src/cardinals.js
index eb7e215..131cbf1 100644
--- a/src/cardinals.js
+++ b/src/cardinals.js
@@ -120,7 +120,8 @@ const cardinals = {
     // everything else: 2, 3, 4, 5, 6, 7, 8, 9, 22, 23, 24, 25, 26, 27, 28, 29,
     // 32, 33, 34, 35, 36, 37, 38, 39, 42, 43, 44, 45, 46, 47, 48, 49, 52, 53,
     // 54, 55, 56, 57, 58, 59, 62, 63, 64, 65, 66, 67, 68, 69, 72, 73, ...
-    n => n % 10 === 1 && n % 100 !== 11 ? 0
+    n => n % 10 === 1 && n % 100 !== 11
+      ? 0
       : n % 10 >= 2 && (n % 100 < 10 || n % 100 >= 20) ? 2 : 1,
 
     // Plural rule #7 (3 forms)
@@ -139,7 +140,8 @@ const cardinals = {
     // 20, 25, 26, 27, 28, 29, 30, 35, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49,
     // 50, 55, 56, 57, 58, 59, 60, 65, 66, 67, 68, 69, 70, 75, 76, 77, ..., 112,
     // 113, ..., 212, 213, ...
-    n => n % 10 === 1 && n % 100 !== 11 ? 0
+    n => n % 10 === 1 && n % 100 !== 11
+      ? 0
       : n % 10 >= 2 && n % 10 <= 4 && (n % 100 < 10 || n % 100 >= 20) ? 1 : 2,
 
     // Plural rule #8 (3 forms)
@@ -165,7 +167,8 @@ const cardinals = {
     // everything else: 0, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
     // 20, 21, 25, 26, 27, 28, 29, 30, 31, 35, 36, 37, 38, 39, 40, 41, 45, 46,
     // 47, 48, 49, 50, 51, 55, 56, 57, 58, 59, 60, 61, 65, 66, 67, 68, ...
-    n => n === 1 ? 0
+    n => n === 1
+      ? 0
       : n % 10 >= 2 && n % 10 <= 4 && (n % 100 < 10 || n % 100 >= 20) ? 1 : 2,
 
     // Plural rule #10 (4 forms)
@@ -207,8 +210,13 @@ const cardinals = {
     // 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, ...
     // ends in 00-02, excluding 0-2: 100, 101, 102, 200, 201, 202, ...
     // is 0: 0
-    n => n === 1 ? 0 : n === 2 ? 1 : n % 100 >= 3 && n % 100 <= 10 ? 2
-      : n % 100 >= 11 ? 3 : n !== 0 ? 4 : 5,
+    n => n === 1
+      ? 0
+      : n === 2
+        ? 1
+        : n % 100 >= 3 && n % 100 <= 10
+          ? 2
+          : n % 100 >= 11 ? 3 : n !== 0 ? 4 : 5,
 
     // Plural rule #13 (4 forms)
     // Families: Semitic (Maltese)
@@ -223,8 +231,11 @@ const cardinals = {
     // everything else: 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
     // 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
     // 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, ...
-    n => n === 1 ? 0 : n === 0 || (n % 100 > 0 && n % 100 < 11) ? 1
-      : n % 100 > 10 && n % 100 < 20 ? 2 : 3,
+    n => n === 1
+      ? 0
+      : n === 0 || (n % 100 > 0 && n % 100 < 11)
+        ? 1
+        : n % 100 > 10 && n % 100 < 20 ? 2 : 3,
 
     // Plural rule #14 (3 forms)
     // Families: Unused
@@ -265,14 +276,18 @@ const cardinals = {
     // 6000000, 7000000, 8000000, 9000000, 10000000, ...
     // everything else: 0, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
     // 20, 25, 26, 27, 28, 30, 35, 36, 37, 38, 40, ...
-    n => n % 10 === 1 && n % 100 !== 11 && n % 100 !== 71 && n % 100 !== 91 ? 0
-      : n % 10 === 2 && n % 100 !== 12 && n % 100 !== 72 && n % 100 !== 92 ? 1
+    n => n % 10 === 1 && n % 100 !== 11 && n % 100 !== 71 && n % 100 !== 91
+      ? 0
+      : n % 10 === 2 && n % 100 !== 12 && n % 100 !== 72 && n % 100 !== 92
+        ? 1
         : (n % 10 === 3 || n % 10 === 4 || n % 10 === 9) &&
           n % 100 !== 13 && n % 100 !== 73 && n % 100 !== 93 &&
           n % 100 !== 14 && n % 100 !== 74 && n % 100 !== 94 &&
-          n % 100 !== 19 && n % 100 !== 79 && n % 100 !== 99 ? 2
-          : n !== 0 && n % 1000000 === 0 ? 3
-            : 4,
+          n % 100 !== 19 && n % 100 !== 79 && n % 100 !== 99
+            ? 2
+            : n !== 0 && n % 1000000 === 0
+              ? 3
+              : 4,
 
     // Plural rule #17 (2 forms)
     // Families: Ecuador indigenous languages (Shuar)
@@ -310,7 +325,8 @@ const cardinals = {
     // 20, 21, 25, 26, 27, 28, 29, 30, 31, 35, 36, 37, 38, 39, 40, 41, 45, 46,
     // 47, 48, 49, 50, 51, 55, 56, 57, 58, 59, 60, 61, 65, 66, 67, 68, 69, 70,
     // 71, 75, 76, 77, ..., 111, 115, ..., 211, 215, ...
-    n => n === 1 ? 0
+    n => n === 1
+      ? 0
       : n % 10 >= 2 && n % 10 <= 4 && (n % 100 < 10 || n % 100 >= 20) ? 1 : 2,
 
     // Plural rule #20 (4 forms)
@@ -338,7 +354,8 @@ const cardinals = {
     // 20, 25, 26, 27, 28, 29, 30, 35, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49,
     // 50, 55, 56, 57, 58, 59, 60, 65, 66, 67, 68, 69, 70, 75, 76, 77, ..., 112,
     // 113, ..., 212, 213, ...
-    n => n % 10 === 1 && n % 100 !== 11 ? 0
+    n => n % 10 === 1 && n % 100 !== 11
+      ? 0
       : n % 10 >= 2 && n % 10 <= 4 && (n % 100 < 10 || n % 100 >= 20) ? 1 : 2,
 
     // Plural rule #22 (3 forms)
diff --git a/src/index.d.ts b/src/index.d.ts
index e97c15f..98f63e8 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -1,20 +1,23 @@
+declare type getPluralFormForCardinal = (count: number) => number
+
 declare function getPluralFormForCardinalByLocale (locale: string, count: number): number
 declare function getPluralFormNameForCardinalByLocale (locale: string, count: number): string
 
 declare function getPluralFormForCardinalByIndex (index: number, count: number): number
 declare function getPluralFormNameForCardinalByIndex (index: number, count: number): string
 
-declare function getPluralRuleForCardinalsByLocale (locale: string): Function
-declare function getPluralRuleForNamedFormsForCardinalsByLocale (locale: string): Function
+declare function getPluralRuleForCardinalsByLocale (locale: string): getPluralFormForCardinal
+declare function getPluralRuleForNamedFormsForCardinalsByLocale (locale: string): getPluralFormForCardinal
 
-declare function getPluralRuleForCardinalsByIndex (index: number): Function
-declare function getPluralRuleForNamedFormsForCardinalsByIndex (index: number): Function
+declare function getPluralRuleForCardinalsByIndex (index: number): getPluralFormForCardinal
+declare function getPluralRuleForNamedFormsForCardinalsByIndex (index: number): getPluralFormForCardinal
 
 export {
   getPluralFormForCardinalByLocale, getPluralRuleForCardinalsByLocale,
   getPluralFormNameForCardinalByLocale, getPluralRuleForNamedFormsForCardinalsByLocale,
   getPluralFormForCardinalByIndex, getPluralRuleForCardinalsByIndex,
-  getPluralFormNameForCardinalByIndex, getPluralRuleForNamedFormsForCardinalsByIndex
+  getPluralFormNameForCardinalByIndex, getPluralRuleForNamedFormsForCardinalsByIndex,
+  getPluralFormForCardinal
 }
 
 export as namespace fastPluralRules
diff --git a/test/browser.html b/test/browser.html
index 1245900..44ec3d2 100644
--- a/test/browser.html
+++ b/test/browser.html
@@ -10,6 +10,7 @@
   <link rel="stylesheet" type="text/css" href="../../node_modules/jasmine-core/lib/jasmine-core/jasmine.css">
   <script src="../../node_modules/jasmine-core/lib/jasmine-core/jasmine.js"></script>
   <script src="../../node_modules/jasmine-core/lib/jasmine-core/jasmine-html.js"></script>
-  <script src="../../node_modules/jasmine-core/lib/jasmine-core/boot.js"></script>
+  <script src="../../node_modules/jasmine-core/lib/jasmine-core/boot0.js"></script>
+  <script src="../../node_modules/jasmine-core/lib/jasmine-core/boot1.js"></script>
 </head>
 </html>
diff --git a/test/browser.test.js b/test/browser.test.js
index f0cd1be..cb317d2 100644
--- a/test/browser.test.js
+++ b/test/browser.test.js
@@ -1,4 +1,4 @@
-/* global jasmine, beforeAll, afterAll, it, expect */
+/* global beforeAll, afterAll, it, expect */
 
 const { join } = require('path')
 const { readdirSync } = require('fs')
@@ -13,20 +13,13 @@ let browser
 let page
 
 const customMatchers = {
-  toPass: function () {
-    return {
-      compare: function (result, message) {
-        return {
-          pass: result,
-          message: () => message
-        }
-      }
-    }
+  toPass: function (pass, message) {
+    return { pass, message }
   }
 }
 
 beforeAll(done => {
-  jasmine.addMatchers(customMatchers)
+  expect.extend(customMatchers)
   server = connect()
     .use(serve(join(__dirname, '..'), { etag: false }))
     .listen(port, () => {
diff --git a/test/documentation.test.js b/test/documentation.test.js
index 4128d30..15348e4 100644
--- a/test/documentation.test.js
+++ b/test/documentation.test.js
@@ -27,7 +27,7 @@ it('form count matches the note in the rule title', () => {
 })
 
 it('locales are assigned to distinct rules', () => {
-  var referredLocales = {}
+  const referredLocales = {}
   descriptions
     .filter(description => description.locales)
     .forEach(description => {
diff --git a/test/typings.test.ts b/test/typings.test.ts
index 66b8372..8535da5 100644
--- a/test/typings.test.ts
+++ b/test/typings.test.ts
@@ -1,14 +1,18 @@
+/* eslint-disable @typescript-eslint/no-unused-vars */
+
 import {
   getPluralFormForCardinalByLocale, getPluralRuleForCardinalsByLocale,
   getPluralFormNameForCardinalByLocale, getPluralRuleForNamedFormsForCardinalsByLocale,
   getPluralFormForCardinalByIndex, getPluralRuleForCardinalsByIndex,
-  getPluralFormNameForCardinalByIndex, getPluralRuleForNamedFormsForCardinalsByIndex
+  getPluralFormNameForCardinalByIndex, getPluralRuleForNamedFormsForCardinalsByIndex,
+  getPluralFormForCardinal
 } from '..'
 
-declare function test (label: string, callback: Function)
+declare type testCallback = () => void
+declare function test (label: string, callback: testCallback): void
 
 test('Type declarations for TypeScript', () => {
-  let rule: Function
+  let rule: getPluralFormForCardinal
   let formIndex: number
   let formName: string
   rule = getPluralRuleForCardinalsByIndex(0)
diff --git a/util/generate-browser-tests.js b/util/generate-browser-tests.js
index 3f6f725..ca275ff 100644
--- a/util/generate-browser-tests.js
+++ b/util/generate-browser-tests.js
@@ -43,7 +43,8 @@ function formatModuleImport (input) {
   if (match[1] === 'cardinals') {
     scriptName = '../cardinals.umd.js'
   } else {
-    scriptName = counter++ % 2 === 0 ? '../../dist/index.umd.min.js'
+    scriptName = counter++ % 2 === 0
+      ? '../../dist/index.umd.min.js'
       : '../../dist/index.umd.js'
   }
   const functionScriptElement = [
diff --git a/util/parse-plural-rule.js b/util/parse-plural-rule.js
index 54aa187..1b13721 100644
--- a/util/parse-plural-rule.js
+++ b/util/parse-plural-rule.js
@@ -14,20 +14,21 @@ function parseNamedList (ruleLines, listName, startIndex = 0) {
   let insideNamedList
   let nextIndex = ruleLines.findIndex((line, index) => {
     if (index < startIndex) {
-      return
+      return false
     }
     const match = /^([^:]+):\s*(.+)$/.exec(line)
     if (match) {
       if (!insideNamedList && match[1] === listName) {
         items.push(match[2])
         insideNamedList = true
-        return
+        return false
       }
       return true
     }
     if (insideNamedList) {
       items.push(line)
     }
+    return false
   })
   if (nextIndex < 0) {
     nextIndex = startIndex