add ESLint

.eslintrc.json

@@ -0,0 +1,31 @@
+{
+  "env": {
+    "browser": true,
+    "es2020": true
+  },
+  "extends": [
+    "eslint:recommended",
+    "plugin:ava/recommended"
+  ],
+  "parserOptions": {
+    "ecmaVersion": 11,
+    "sourceType": "module"
+  },
+  "plugins": [
+    "ava"
+  ],
+  "rules": {
+    "indent": [
+      "error",
+      2
+    ],
+    "quotes": [
+      "error",
+      "single"
+    ],
+    "semi": [
+      "error",
+      "never"
+    ]
+  }
+}

README.md

@@ -28,5 +28,6 @@ More details can be found in the [WordPress Plugin Directory](https://wordpress.
 10. Tag the new version in `git` too.
 
 ### Other commands
+- Run ESLint: `npm run eslint`
 - Run tests: `npm test`
 - Delete build folder: `gulp clean`

gulpfile.js

@@ -32,7 +32,7 @@ function bundleFrontend() {
       },
     }))
     .pipe(dest(FOLDER_BUILD));
-  }
+}
 
 function copyBackend() {
   return src([

package.json

@@ -6,6 +6,7 @@
   "scripts": {
     "build-dev": "gulp dev",
     "build-prod": "ava && gulp prod",
+    "eslint": "npx eslint source/**/*.js",
     "test": "ava"
   },
   "author": {
@@ -26,6 +27,8 @@
   "devDependencies": {
     "ava": "^3.15.0",
     "del": "^6.0.0",
+    "eslint": "^7.23.0",
+    "eslint-plugin-ava": "^12.0.0",
     "esm": "^3.2.25",
     "gulp": "^4.0.2",
     "gulp-replace": "^1.0.0",