fix: bundle generation for cjs

rollup.config.js

@@ -8,10 +8,10 @@ const { version } = require('./package.json');
 // -- Config ------------------------------------------------------------------
 const input = path.resolve(__dirname, 'src/main.ts');
 const umdDir = path.resolve(__dirname, 'dist/umd');
+const cjsDir = path.resolve(__dirname, 'dist/commonjs');
 const modulesDir = path.resolve(__dirname, 'dist/modules');
 const banner = (`/**\n * Copyright (C) 2017 salesforce.com, inc.\n */`);
 const footer = `/** version: ${version} */`;
-const prodToken = JSON.stringify('production');
 
 // -- Helpers -----------------------------------------------------------------
 function inlineMinifyPlugin() {
@@ -23,14 +23,15 @@ function inlineMinifyPlugin() {
 }
 
 function rollupConfig({ formats, prod }) {
+    const replaceToken = JSON.stringify(prod ? 'production' : 'development');
     const plugins = [
         typescript({ target: 'es6', typescript: require('typescript') }),
-        prod && replace({ 'process.env.NODE_ENV': prodToken }),
+        prod !== undefined && replace({ 'process.env.NODE_ENV': replaceToken }),
         prod && inlineMinifyPlugin({})
     ].filter(Boolean);
 
     const output = formats.map(format => {
-        const targetDirectory = format === 'umd' ? umdDir : modulesDir;
+        const targetDirectory = format === 'umd' ? umdDir : format === 'cjs' ? cjsDir : modulesDir;
         const targetName = `observable-membrane${prod ? '.min' : '' }.js`;
 
         return {
@@ -48,6 +49,7 @@ function rollupConfig({ formats, prod }) {
 // -- Rollup ------------------------------------------------------------------
 
 module.exports = [
-    rollupConfig({ formats: ['umd', 'es'], prod: false }),
+    rollupConfig({ formats: ['cjs', 'es'] }),
+    rollupConfig({ formats: ['umd'], prod: false }),
     rollupConfig({ formats: ['umd'], prod: true })
 ];