add babel and rollup

rudder-client-javascript/.babelrc

@@ -0,0 +1,14 @@
+{
+  "presets": [
+    [
+      "@babel/env",
+      {
+        "modules": false,
+        "useBuiltIns": "usage",
+        "targets": {
+          "node": "4"
+        }
+      }
+    ]
+  ]
+}

rudder-client-javascript/package.json

@@ -10,7 +10,8 @@
   "author": "",
   "license": "ISC",
   "devDependencies": {
-    "jest": "^24.9.0",
+    "@babel/core": "^7.6.2",
+    "@babel/preset-env": "^7.6.2",
     "eslint": "^6.1.0",
     "eslint-config-airbnb": "^18.0.1",
     "eslint-config-prettier": "^6.2.0",
@@ -19,6 +20,10 @@
     "eslint-plugin-prettier": "^3.1.0",
     "eslint-plugin-react": "^7.14.3",
     "eslint-plugin-react-hooks": "^1.7.0",
-    "prettier": "^1.18.2"
+    "jest": "^24.9.0",
+    "prettier": "^1.18.2",
+    "rollup-plugin-babel": "^4.3.3",
+    "rollup-plugin-commonjs": "^10.1.0",
+    "rollup-plugin-node-resolve": "^5.2.0"
   }
 }

rudder-client-javascript/rollup.config.js

@@ -0,0 +1,25 @@
+import babel from "rollup-plugin-babel";
+import commonjs from "rollup-plugin-commonjs";
+import resolve from "rollup-plugin-node-resolve";
+
+export default {
+  input: "RudderClient.js",
+  output: [
+    {
+      file: "dist/bundle_iife.js",
+      format: "iife",
+      name: "analytics"
+    },
+    {
+      file: "dist/bundle_cjs.js",
+      format: "cjs"
+    }
+  ],
+  plugins: [
+    resolve(),
+    commonjs(),
+    babel({
+      exclude: "node_modules/**"
+    })
+  ]
+};