Arrow function style

.eslintrc.json

@@ -8,7 +8,7 @@
     "browser": true,
     "node": false
   },
-  "plugins": ["deprecation", "cypress", "jest", "simple-import-sort", "@typescript-eslint"],
+  "plugins": ["deprecation", "cypress", "jest", "prefer-arrow", "simple-import-sort", "@typescript-eslint"],
   "extends": [
     "eslint:recommended",
     "plugin:@typescript-eslint/recommended",
@@ -18,8 +18,13 @@
     "plugin:svelte/prettier"
   ],
   "rules": {
+    "arrow-body-style": ["error", "as-needed"],
     "deprecation/deprecation": "warn",
     "no-warning-comments": "warn",
+    "prefer-arrow/prefer-arrow-functions": [
+      "error",
+      { "allowStandaloneDeclarations": true }
+    ],
     "simple-import-sort/imports": "error",
     "simple-import-sort/exports": "error",
     "@typescript-eslint/array-type": ["error", { "default": "generic" }],

gulpfile.js

@@ -6,25 +6,25 @@ const filter = require("gulp-filter");
 const replace = require("gulp-replace");
 const webpack = require("webpack-stream");
 
-gulp.task("build:appsscript", function () {
-  return gulp.src("src/appsscript.json").pipe(gulp.dest("dist/"));
-});
+gulp.task("build:appsscript", () =>
+  gulp.src("src/appsscript.json").pipe(gulp.dest("dist/"))
+);
 
-gulp.task("build:frontend", function () {
-  return gulp
+gulp.task("build:frontend", () =>
+  gulp
     .src("src/frontend/index.ts")
     .pipe(webpack(require("./frontend.webpack.config.js")(undefined, {})))
     .pipe(filter(["index.html"]))
     .pipe(replace("\u0085", "\\u0085"))
-    .pipe(gulp.dest("dist/"));
-});
+    .pipe(gulp.dest("dist/"))
+);
 
-gulp.task("build:backend", function () {
-  return gulp
+gulp.task("build:backend", () =>
+  gulp
     .src("src/backend/index.ts")
     .pipe(webpack(require("./backend.webpack.config.js")))
-    .pipe(gulp.dest("dist/"));
-});
+    .pipe(gulp.dest("dist/"))
+);
 
 gulp.task(
   "build",