Add JavaScript linting (#82)

.eslintrc

+{
+  "extends": "eslint:recommended",
+  "rules": {
+    "semi": ["error", "never"],
+    "quotes": ["error", "double"],
+    "no-unused-vars": ["error", { "vars": "all", "args": "none" }]
+  },
+  "plugins": [
+    "import"
+  ],
+  "env": {
+    "browser": true,
+    "es6": true
+  },
+  "parserOptions": {
+    "ecmaVersion": 6,
+    "sourceType": "module"
+  }
+}

.travis.yml

@@ -2,14 +2,24 @@ language: ruby
 sudo: false
 bundler: true
 
-script: bundle exec rake
-
 rvm:
   - 2.3
   - 2.4
   - ruby-head
 
+cache:
+  bundler: true
+  yarn: true
+
 matrix:
   allow_failures:
     - rvm: ruby-head
   fast_finish: true
+
+install:
+  - bundle install
+  - yarn install
+
+script:
+  - bundle exec rake
+  - yarn lint

app/javascript/activestorage/blob_upload.js

@@ -19,7 +19,7 @@ export class BlobUpload {
   requestDidLoad(event) {
     const { status, response } = this.xhr
     if (status >= 200 && status < 300) {
-      this.callback(null, this.xhr.response)
+      this.callback(null, response)
     } else {
       this.requestDidError(event)
     }

package.json

@@ -10,6 +10,8 @@
     "babel-core": "^6.25.0",
     "babel-loader": "^7.1.1",
     "babel-preset-env": "^1.6.0",
+    "eslint": "^4.3.0",
+    "eslint-plugin-import": "^2.7.0",
     "spark-md5": "^3.0.0",
     "webpack": "^3.4.0"
   },
@@ -17,6 +19,8 @@
     "app/assets/javascripts/activestorage.js"
   ],
   "scripts": {
-    "build": "webpack -p"
+    "prebuild": "yarn lint",
+    "build": "webpack -p",
+    "lint": "eslint app/javascript"
   }
 }