make eslint manual fixes

Author: lukasvice

src/index.ts

@@ -43,18 +43,18 @@ class Internationalization<T extends string> {
     // If the DOM isn't accessible the website may be rendered on a server
     if (canUseDOM()) {
       // Get browser language
-      let browserLanguage =
-        (navigator.languages && navigator.languages[0]) || navigator.language
+      // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+      let browserLanguage = navigator.languages?.[0] || navigator.language
 
       // Check if the browser language is in the format of xx-XX, extract the first part
-      if (/^[a-zA-z]{2}\-/.test(browserLanguage)) {
+      if (/^[a-zA-z]{2}-/.test(browserLanguage)) {
         browserLanguage = browserLanguage.substring(0, 2)
       }
 
       return (
         this.supportedLanguages.find((lang) =>
           isEqualCaseInsensitive(lang, browserLanguage),
-        ) || this.fallbackLanguage
+        ) ?? this.fallbackLanguage
       )
     }
 
@@ -74,7 +74,7 @@ class Internationalization<T extends string> {
       const cookieLanguage =
         this.supportedLanguages.find((lang) =>
           isEqualCaseInsensitive(lang, language),
-        ) || this.fallbackLanguage
+        ) ?? this.fallbackLanguage
 
       setCookie(this.cookieName, cookieLanguage)
     }
@@ -103,7 +103,7 @@ class Internationalization<T extends string> {
       // Get accept language from request header
       const acceptLanguage = request.headers['accept-language']
 
-      if (acceptLanguage) {
+      if (acceptLanguage && typeof acceptLanguage === 'string') {
         // Extract the locale string and the priority from header string
         const requestedLocales = acceptLanguage.split(',').map((part) => {
           const [locale, priority] = part.trim().split(';q=')
@@ -135,15 +135,15 @@ class Internationalization<T extends string> {
       const language = getCookieFromDocument(this.cookieName)
 
       // If cookie is undefined get the language form the browser
-      if (language == undefined) {
+      if (language === undefined) {
         return this.detectBrowserLanguage()
       }
 
       // Return found language or fallback language
       return (
         this.supportedLanguages.find((lang) =>
           isEqualCaseInsensitive(lang, language),
-        ) || this.fallbackLanguage
+        ) ?? this.fallbackLanguage
       )
     }
 

src/utilities.ts

@@ -29,7 +29,7 @@ function getCookieFromRequest(
   name: string,
   request: IncomingMessage,
 ): string | undefined {
-  if (request.headers?.cookie) {
+  if (request.headers.cookie) {
     const pattern = getCookiePattern(name)
     const matched = request.headers.cookie.match(pattern)
 
@@ -59,9 +59,8 @@ function setCookie(name: string, value: string): void {
  */
 function canUseDOM(): boolean {
   return Boolean(
-    typeof window !== 'undefined' &&
-      window.document &&
-      window.document.createElement,
+    // eslint-disable-next-line @typescript-eslint/unbound-method, @typescript-eslint/no-unnecessary-condition, @typescript-eslint/no-deprecated
+    typeof window !== 'undefined' && window.document?.createElement,
   )
 }
 

tsconfig.json

@@ -6,7 +6,8 @@
     "declaration": true,
     "outDir": "./dist",
     "strict": true,
-    "esModuleInterop": true
+    "esModuleInterop": true,
+    "types": ["node", "jest"]
   },
   "include": ["src"],
   "exclude": ["node_modules", "**/__test__/*", "**/__tests__/*"]