Fix eslint warnings and add eslint check in CI

.eslintrc.json

@@ -0,0 +1,95 @@
+{
+    "env": {
+        "browser": true,
+        "node": true,
+        "es6": true
+    },
+    "extends": "eslint:recommended",
+    "globals": {
+        "module": "readonly",
+        "require": "readonly"
+    },
+    "parserOptions": {
+        "ecmaVersion": 2018,
+        "requireConfigFile": false,
+        "sourceType": "module"
+    },
+    "ignorePatterns": ["**min.js", "**/highlight.js", "**/playground_editor/*"],
+    "rules": {
+        "indent": [
+            "error",
+            4
+        ],
+        "linebreak-style": [
+            "error",
+            "unix"
+        ],
+        "quotes": [
+            "error",
+            "single"
+        ],
+        "semi": [
+            "error",
+            "always"
+        ],
+        "brace-style": [
+            "error",
+            "1tbs",
+            { "allowSingleLine": false }
+        ],
+        "curly": "error",
+        "no-trailing-spaces": "error",
+        "no-multi-spaces": "error",
+        "keyword-spacing": [
+            "error",
+            { "before": true, "after": true }
+        ],
+        "comma-spacing": [
+            "error",
+            { "before": false, "after": true }
+        ],
+        "arrow-spacing": [
+            "error",
+            { "before": true, "after": true }
+        ],
+        "key-spacing": [
+            "error",
+            { "beforeColon": false, "afterColon": true, "mode": "strict" }
+        ],
+        "func-call-spacing": ["error", "never"],
+        "space-infix-ops": "error",
+        "space-before-function-paren": ["error", "never"],
+        "space-before-blocks": "error",
+        "no-console": [
+            "error",
+            { "allow": ["warn", "error"] }
+        ],
+        "comma-dangle": ["error", "always-multiline"],
+        "comma-style": ["error", "last"],
+        "max-len": ["error", { "code": 100, "tabWidth": 2 }],
+        "eol-last": ["error", "always"],
+        "no-extra-parens": "error",
+        "arrow-parens": ["error", "as-needed"],
+        "no-unused-vars": [
+            "error",
+            {
+                "argsIgnorePattern": "^_",
+                "varsIgnorePattern": "^_"
+            }
+        ],
+        "prefer-const": ["error"],
+        "no-var": "error",
+        "eqeqeq": "error"
+    },
+    "overrides": [
+        {
+            "files": [
+                "tests/**/*.js"
+            ],
+            "env": {
+                "jest": true,
+                "node": true
+            }
+        }
+    ]
+}

.github/workflows/main.yml

@@ -3,9 +3,6 @@ on:
   pull_request:
   merge_group:
 
-env:
-  BROWSER_UI_TEST_VERSION: '0.19.0'
-
 jobs:
   test:
     runs-on: ${{ matrix.os }}
@@ -85,7 +82,9 @@ jobs:
         with:
           node-version: 20
       - name: Install browser-ui-test
-        run: npm install browser-ui-test@"${BROWSER_UI_TEST_VERSION}"
+        run: npm install
+      - name: Run eslint
+        run: npm run lint
       - name: Build and run tests (+ GUI)
         run: cargo test --locked --target x86_64-unknown-linux-gnu --test gui
 

CONTRIBUTING.md

@@ -150,7 +150,8 @@ If you want to only run some tests, you can filter them by passing (part of) the
 cargo test --test gui -- search
 ```
 
-The first time, it'll fail and ask you to install the `browser-ui-test` package. Install it then re-run the tests.
+The first time, it'll fail and ask you to install the `browser-ui-test` package. Install it with the provided
+command then re-run the tests.
 
 If you want to disable the headless mode, use the `--disable-headless-test` option:
 
@@ -162,6 +163,21 @@ The GUI tests are in the directory `tests/gui` in text files with the `.goml` ex
 using a `node.js` framework called `browser-ui-test`. You can find documentation for this language on its
 [repository](https://github.com/GuillaumeGomez/browser-UI-test/blob/master/goml-script.md).
 
+### Checking changes in `.js` files
+
+The `.js` files source code is checked using [`eslint`](https://eslint.org/). This is a linter (just like `clippy` in Rust)
+for the Javascript language. You can install it with `npm` by running the following command:
+
+```
+npm install
+```
+
+Then you can run it using:
+
+```
+npm run lint
+```
+
 ## Updating highlight.js
 
 The following are instructions for updating [highlight.js](https://highlightjs.org/).

package.json

@@ -0,0 +1,10 @@
+{
+  "dependencies": {
+    "browser-ui-test": "0.19.0",
+    "eslint": "^8.57.1"
+  },
+  "scripts": {
+    "lint": "eslint src/theme/*js src/theme/**/*js",
+    "lint-fix": "eslint --fix src/theme/*js src/theme/**/*js"
+  }  
+}