feat(import): enforce no extensions for js files

rules/base.js

@@ -261,6 +261,7 @@ module.exports = {
     'import/no-commonjs': ['error'],
     'import/no-extraneous-dependencies': ['error'],
     'import/no-duplicates': ['error'],
+    'import/extensions': [2, 'always', { js: 'never' }],
     'prettier/prettier': [
       'error',
       { trailingComma: 'es5', singleQuote: true, printWidth: 80 },

sample-project/index.js

@@ -1,4 +1,4 @@
-import connect from './src/connect.js';
-import Provider from './src/Provider.js';
+import connect from './src/connect';
+import Provider from './src/Provider';
 
 export { Provider, connect };

sample-project/src/Provider.js

@@ -1,8 +1,8 @@
 import { Component, Children } from 'react';
 import PropTypes from 'prop-types';
 
-import createStore from './createStore.js';
-import storeShape from './storeShape.js';
+import createStore from './createStore';
+import storeShape from './storeShape';
 
 class Provider extends Component {
   static propTypes = {

sample-project/src/connect.js

@@ -1,7 +1,7 @@
 import React, { Component } from 'react';
 import shallowCompare from 'react-addons-shallow-compare';
 
-import storeShape from './storeShape.js';
+import storeShape from './storeShape';
 
 const getDisplayName = WrappedComponent =>
   WrappedComponent.displayName || WrappedComponent.name || 'UnknownComponent';