fix eslint on js files

src/components/Navigation.tsx

@@ -6,7 +6,7 @@ import Icon, { IconType } from "./Icon";
 import NavbarDropdownLink from "./NavbarDropdownLink";
 import NavbarChildLink from "./NavbarChildLink";
 
-export const renderNavigationItems = (mobile = false) => (
+export const renderNavigationItems = (mobile = false): JSX.Element => (
   <>
     <NavbarDropdownLink to="/kilta" text="Kilta ›" exploded={mobile}>
       <NavbarChildLink to="/kilta/toiminta">Toiminta</NavbarChildLink>

src/components/Widgets/SignupQuestionsWidget/TypeWidget.tsx

@@ -7,15 +7,15 @@ interface TypeWidgetProps {
 }
 
 class TypeWidget extends React.Component<TypeWidgetProps> {
-  handleTypeChange = (questions: Question[], index: number) => (event) => {
+  handleTypeChange = (questions: Question[], index: number): React.ChangeEventHandler<HTMLSelectElement> => (event) => {
     const { onChange } = this.props;
-    const val = event.target.value;
+    const val = event.target.value as Question["type"];
     // eslint-disable-next-line no-param-reassign
     questions[index].type = val;
     onChange(questions);
   };
 
-  render() {
+  render(): JSX.Element {
     const { inputProps } = this.props;
     const { type, questions, index } = inputProps;
     const options = optionTypes.map((t) => (

src/pages/_document.tsx

@@ -1,13 +1,13 @@
 import React from "react";
 import Document, {
-  Html, Head, Main, NextScript, DocumentContext,
+  Html, Head, Main, NextScript, DocumentContext, DocumentInitialProps,
 } from "next/document";
 import { ServerStyleSheet } from "styled-components";
 import Favicons from "@components/Favicons";
 import HTMLLogo from "@components/HTMLLogo";
 
 export default class MyDocument extends Document<{ styleTags: unknown }> {
-  static async getInitialProps(ctx: DocumentContext) {
+  static async getInitialProps(ctx: DocumentContext): Promise<DocumentInitialProps> {
     const sheet = new ServerStyleSheet();
     const originalRenderPage = ctx.renderPage;
     try {