chore: Add ESLint to project and fix issues reported

.eslintrc.json

@@ -0,0 +1,6 @@
+{
+	"extends": [
+		"@nextcloud/eslint-config/typescript"
+	],
+	"ignorePatterns": [ "dist/**" ]
+}

.github/workflows/lint-eslint.yml

@@ -0,0 +1,96 @@
+# This workflow is provided via the organization template repository
+#
+# https://github.com/nextcloud/.github
+# https://docs.github.com/en/actions/learn-github-actions/sharing-workflows-with-your-organization
+#
+# Use lint-eslint together with lint-eslint-when-unrelated to make eslint a required check for GitHub actions
+# https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/troubleshooting-required-status-checks#handling-skipped-but-required-checks
+
+name: Lint eslint
+
+on:
+  pull_request:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: lint-eslint-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  changes:
+    runs-on: ubuntu-latest
+
+    outputs:
+      src: ${{ steps.changes.outputs.src}}
+
+    steps:
+      - uses: dorny/paths-filter@4512585405083f25c027a35db413c2b3b9006d50 # v2.11.1
+        id: changes
+        continue-on-error: true
+        with:
+          filters: |
+            src:
+              - '.github/workflows/**'
+              - '**/src/**'
+              - '**/appinfo/info.xml'
+              - 'package.json'
+              - 'package-lock.json'
+              - 'tsconfig.json'
+              - '.eslintrc.*'
+              - '.eslintignore'
+              - '**.js'
+              - '**.ts'
+              - '**.vue'
+
+  lint:
+    runs-on: ubuntu-latest
+
+    needs: changes
+    if: needs.changes.outputs.src != 'false'
+
+    name: NPM lint
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+
+      - name: Read package.json node and npm engines version
+        uses: skjnldsv/read-package-engines-version-actions@8205673bab74a63eb9b8093402fd9e0e018663a1 # v2.2
+        id: versions
+        with:
+          fallbackNode: '^20'
+          fallbackNpm: '^9'
+
+      - name: Set up node ${{ steps.versions.outputs.nodeVersion }}
+        uses: actions/setup-node@b39b52d1213e96004bfcb1c61a8a6fa8ab84f3e8 # v4.0.1
+        with:
+          node-version: ${{ steps.versions.outputs.nodeVersion }}
+
+      - name: Set up npm ${{ steps.versions.outputs.npmVersion }}
+        run: npm i -g npm@"${{ steps.versions.outputs.npmVersion }}"
+
+      - name: Install dependencies
+        env:
+          CYPRESS_INSTALL_BINARY: 0
+          PUPPETEER_SKIP_DOWNLOAD: true
+        run: npm ci
+
+      - name: Lint
+        run: npm run lint
+
+  summary:
+    permissions:
+      contents: none
+    runs-on: ubuntu-latest
+    needs: [changes, lint]
+
+    if: always()
+
+    # This is the summary, we just avoid to rename it so that branch protection rules still match
+    name: eslint
+
+    steps:
+      - name: Summary status
+        run: if ${{ needs.changes.outputs.src != 'false' && needs.lint.result != 'success' }}; then exit 1; fi

babel.config.js

@@ -1,12 +1,12 @@
 module.exports = {
-    presets: [
-        "@babel/typescript",
-        [
-            "@babel/env",
-            {
-                useBuiltIns: "usage",
-                corejs: "3.0.0",
-            },
-        ],
-    ]
-};
+	presets: [
+		'@babel/typescript',
+		[
+			'@babel/env',
+			{
+				useBuiltIns: 'usage',
+				corejs: '3.0.0',
+			},
+		],
+	],
+}