Improve linting rules

- Disallow undeclared variables

- Disallow unused variables

- Suggest using const

- Enforce a convention in module import order

- Enable Node env for linting

- Require a space before function parenthesis in non-named functions

.eslintrc

@@ -1,3 +1,6 @@
 {
   "extends": "./index.js",
+  "env": {
+    "node": true
+  }
 }

rules/es2015/style.js

@@ -26,6 +26,10 @@ module.exports = {
     // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-webpack-loader-syntax.md
     'import/no-webpack-loader-syntax': 'error',
 
+    // Enforce a convention in module import order
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/order.md
+    'import/order': 'error',
+
     // Require modules with a single export to use a default export
     // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/prefer-default-export.md
     'import/prefer-default-export': 'error',
@@ -42,6 +46,10 @@ module.exports = {
     // http://eslint.org/docs/rules/no-var
     'no-var': 'error',
 
+    // Suggest using const
+    // https://eslint.org/docs/rules/prefer-const
+    'prefer-const': 'error',
+
     // Require template literals instead of string concat
     // http://eslint.org/docs/rules/prefer-template
     'prefer-template': 'error',

rules/general/error.js

@@ -4,7 +4,15 @@ module.exports = {
 
     // Ensure RegExp strings are valid
     // http://eslint.org/docs/rules/no-invalid-regexp
-    'no-invalid-regexp': 'error'
+    'no-invalid-regexp': 'error',
+
+    // Disallow undeclared variables
+    // https://eslint.org/docs/rules/no-undef
+    'no-undef': 'error',
+
+    // Disallow unused variables
+    // https://eslint.org/docs/rules/no-unused-vars
+    'no-unused-vars': 'error',
 
   }
 

rules/general/format.js

@@ -128,6 +128,14 @@ module.exports = {
     // http://eslint.org/docs/rules/space-before-blocks
     'space-before-blocks': ['error', 'always'],
 
+    // Require a space before function parenthesis in non-named functions
+    // https://eslint.org/docs/rules/space-before-function-paren
+    'space-before-function-paren': ['error', {
+      anonymous: 'always',
+      named: 'never',
+      asyncArrow: 'always'
+    }],
+
     // Prohibit spaces inside parens (immediately adjacent to paren)
     // http://eslint.org/docs/rules/space-in-parens
     'space-in-parens': ['error', 'never'],