diff --git a/karma.conf.js b/karma.conf.js
index 269767d50..cc2feda57 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -6,10 +6,10 @@ module.exports = function(config) {
     files: [
       'c3.css',
       'spec/*-helper.js',
-      'spec/*-spec.js'
+      'spec/*.js'
     ],
     preprocessors: {
-      'spec/c3-helper.js': ['browserify']
+      'spec/*.js': ['browserify']
     },
     browserify: {
       debug: true,
diff --git a/package-lock.json b/package-lock.json
index 17a11baa9..2904e2204 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "c3",
-  "version": "0.4.13",
+  "version": "0.4.14",
   "lockfileVersion": 1,
   "dependencies": {
     "abbrev": {
@@ -297,6 +297,12 @@
       "integrity": "sha1-NRV7EBQm/S/9PaP3XH0ekYNbv4o=",
       "dev": true
     },
+    "babel-plugin-external-helpers": {
+      "version": "6.22.0",
+      "resolved": "https://registry.npmjs.org/babel-plugin-external-helpers/-/babel-plugin-external-helpers-6.22.0.tgz",
+      "integrity": "sha1-IoX0iwK9Xe3oUXXK+MYuhq3M76E=",
+      "dev": true
+    },
     "babel-plugin-istanbul": {
       "version": "4.1.4",
       "resolved": "https://registry.npmjs.org/babel-plugin-istanbul/-/babel-plugin-istanbul-4.1.4.tgz",
@@ -1292,6 +1298,12 @@
       "integrity": "sha1-/cpRzuYTOJXjyI1TXOSdv/YqRjM=",
       "dev": true
     },
+    "estree-walker": {
+      "version": "0.2.1",
+      "resolved": "https://registry.npmjs.org/estree-walker/-/estree-walker-0.2.1.tgz",
+      "integrity": "sha1-va/oCVOD2EFNXcLs9MkXO225QS4=",
+      "dev": true
+    },
     "esutils": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/esutils/-/esutils-2.0.2.tgz",
@@ -3680,6 +3692,18 @@
       "integrity": "sha1-4NBUl4d6OYwQTYFtJzOnGKepTio=",
       "dev": true
     },
+    "rollup-plugin-babel": {
+      "version": "2.7.1",
+      "resolved": "https://registry.npmjs.org/rollup-plugin-babel/-/rollup-plugin-babel-2.7.1.tgz",
+      "integrity": "sha1-FlKBl7D5OKFTb0RoPHqT1XMYL1c=",
+      "dev": true
+    },
+    "rollup-pluginutils": {
+      "version": "1.5.2",
+      "resolved": "https://registry.npmjs.org/rollup-pluginutils/-/rollup-pluginutils-1.5.2.tgz",
+      "integrity": "sha1-HhVud4+UtyVb+hs9AXi+j1xVJAg=",
+      "dev": true
+    },
     "safe-buffer": {
       "version": "5.0.1",
       "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.0.1.tgz",
diff --git a/package.json b/package.json
index 4b820dea9..96c93492f 100644
--- a/package.json
+++ b/package.json
@@ -8,7 +8,7 @@
     "lint": "jshint --reporter=node_modules/jshint-stylish src/ spec/",
     "build": "npm run build:js && npm run build:css",
     "build:js": "npm run build:js:rollup && npm run build:js:uglify",
-    "build:js:rollup": "rollup -f umd --name c3 --globals d3:d3 src/index.js > c3.js",
+    "build:js:rollup": "rollup -c > c3.js",
     "build:js:uglify": "uglifyjs c3.js --compress --mangle -o c3.min.js",
     "build:css": "npm run build:css:sass && npm run build:css:min",
     "build:css:sass": "node-sass src/scss/main.scss > c3.css",
@@ -41,6 +41,7 @@
     "d3": "~3.5.0"
   },
   "devDependencies": {
+    "babel-plugin-external-helpers": "^6.22.0",
     "babel-plugin-istanbul": "^4.1.4",
     "babel-preset-es2015": "^6.24.1",
     "babelify": "^7.3.0",
@@ -60,12 +61,14 @@
     "node-static": "^0.7.9",
     "nodemon": "^1.11.0",
     "rollup": "^0.41.6",
+    "rollup-plugin-babel": "^2.7.1",
     "uglify-js": "^3.0.15",
     "watchify": "^3.9.0"
   },
   "nyc": {
     "exclude": [
-      "src/polyfill.js"
+      "src/polyfill.js",
+      "spec/"
     ]
   }
 }
diff --git a/rollup.config.js b/rollup.config.js
new file mode 100644
index 000000000..7f14b76f7
--- /dev/null
+++ b/rollup.config.js
@@ -0,0 +1,15 @@
+import babel from 'rollup-plugin-babel';
+
+export default {
+    entry: 'src/index.js',
+    format: 'umd',
+    moduleName: 'c3',
+    plugins: [babel({
+        presets: [['es2015', {
+            modules: false
+        }]],
+        plugins: [
+            'external-helpers'
+        ]
+    })]
+};
diff --git a/spec/data.convert.js b/spec/data.convert.js
new file mode 100644
index 000000000..d5d38bb8e
--- /dev/null
+++ b/spec/data.convert.js
@@ -0,0 +1,97 @@
+import c3 from '../src';
+
+const $$ = c3.chart.internal.fn;
+
+describe('$$.convertColumnsToData', () => {
+    it('converts column data to normalized data', () => {
+        const data = $$.convertColumnsToData([
+            ["cat1", "a", "b", "c", "d"],
+            ["data1", 30, 200, 100, 400],
+            ["cat2", "b", "a", "c", "d", "e", "f"],
+            ["data2", 400, 60, 200, 800, 10, 10]
+        ]);
+
+        expect(data).toEqual([{
+            cat1: 'a',
+            data1: 30,
+            cat2: 'b',
+            data2: 400
+        }, {
+            cat1: 'b',
+            data1: 200,
+            cat2: 'a',
+            data2: 60
+        }, {
+            cat1: 'c',
+            data1: 100,
+            cat2: 'c',
+            data2: 200
+        }, {
+            cat1: 'd',
+            data1: 400,
+            cat2: 'd',
+            data2: 800
+        }, {
+            cat2: 'e',
+            data2: 10
+        }, {
+            cat2: 'f',
+            data2: 10
+        }]);
+    });
+
+    it('throws when the column data contains undefined', () => {
+        expect(() => $$.convertColumnsToData([
+            ["cat1", "a", "b", "c", "d"],
+            ["data1", undefined]
+        ])).toThrowError(Error, /Source data is missing a component/);
+    });
+});
+
+describe('$$.convertRowsToData', () => {
+    it('converts the row data to normalized data', () => {
+        const data = $$.convertRowsToData([
+            ['data1', 'data2', 'data3'],
+            [90, 120, 300],
+            [40, 160, 240],
+            [50, 200, 290],
+            [120, 160, 230],
+            [80, 130, 300],
+            [90, 220, 320]
+        ]);
+
+        expect(data).toEqual([{
+            data1: 90,
+            data2: 120,
+            data3: 300
+        }, {
+            data1: 40,
+            data2: 160,
+            data3: 240
+        }, {
+            data1: 50,
+            data2: 200,
+            data3: 290
+        }, {
+            data1: 120,
+            data2: 160,
+            data3: 230
+        }, {
+            data1: 80,
+            data2: 130,
+            data3: 300
+        }, {
+            data1: 90,
+            data2: 220,
+            data3: 320
+        }]);
+    });
+
+    it('throws when the row data contains undefined', () => {
+        expect(() => $$.convertRowsToData([
+            ['data1', 'data2', 'data3'],
+            [40, 160, 240],
+            [90, 120, undefined]
+        ])).toThrowError(Error, /Source data is missing a component/);
+    });
+});
diff --git a/spec/shape.line-spec.js b/spec/shape.line-spec.js
index 6d6a65d96..9c8df3464 100644
--- a/spec/shape.line-spec.js
+++ b/spec/shape.line-spec.js
@@ -1,3 +1,5 @@
+import { parseSvgPath } from './svg-helper';
+
 describe('c3 chart shape line', function () {
     'use strict';
 
@@ -7,8 +9,6 @@ describe('c3 chart shape line', function () {
         chart = window.initChart(chart, args, done);
     });
 
-    var parseSvgPath = window.parseSvgPath;
-
     describe('shape-rendering for line chart', function () {
 
         beforeAll(function () {
diff --git a/spec/svg-helper.js b/spec/svg-helper.js
index c1f2b4906..5a07768a1 100644
--- a/spec/svg-helper.js
+++ b/spec/svg-helper.js
@@ -3,8 +3,7 @@
  * @param  {String} d SvgPath d attribute.]
  * @return {Array} an array of drawing commands.
  */
-
-function parseSvgPath(d) { //jshint ignore:line
+export function parseSvgPath(d) { //jshint ignore:line
     'use strict';
 
     var commands = [];
diff --git a/src/data.convert.js b/src/data.convert.js
index 34808a90b..0edac365a 100644
--- a/src/data.convert.js
+++ b/src/data.convert.js
@@ -89,36 +89,53 @@ c3_chart_internal_fn.findValueInJson = function (object, path) {
     }
     return object;
 };
-c3_chart_internal_fn.convertRowsToData = function (rows) {
-    var keys = rows[0], new_row = {}, new_rows = [], i, j;
-    for (i = 1; i < rows.length; i++) {
-        new_row = {};
-        for (j = 0; j < rows[i].length; j++) {
+
+/**
+ * Converts the rows to normalized data.
+ * @param {any[][]} rows The row data
+ * @return {Object[]}
+ */
+c3_chart_internal_fn.convertRowsToData = (rows) => {
+    const newRows = [];
+    const keys = rows[0];
+
+    for (let i = 1; i < rows.length; i++) {
+        const newRow = {};
+        for (let j = 0; j < rows[i].length; j++) {
             if (isUndefined(rows[i][j])) {
                 throw new Error("Source data is missing a component at (" + i + "," + j + ")!");
             }
-            new_row[keys[j]] = rows[i][j];
+            newRow[keys[j]] = rows[i][j];
         }
-        new_rows.push(new_row);
+        newRows.push(newRow);
     }
-    return new_rows;
+    return newRows;
 };
-c3_chart_internal_fn.convertColumnsToData = function (columns) {
-    var new_rows = [], i, j, key;
-    for (i = 0; i < columns.length; i++) {
-        key = columns[i][0];
-        for (j = 1; j < columns[i].length; j++) {
-            if (isUndefined(new_rows[j - 1])) {
-                new_rows[j - 1] = {};
+
+/**
+ * Converts the columns to normalized data.
+ * @param {any[][]} columns The column data
+ * @return {Object[]}
+ */
+c3_chart_internal_fn.convertColumnsToData = (columns) => {
+    const newRows = [];
+
+    for (let i = 0; i < columns.length; i++) {
+        const key = columns[i][0];
+        for (let j = 1; j < columns[i].length; j++) {
+            if (isUndefined(newRows[j - 1])) {
+                newRows[j - 1] = {};
             }
             if (isUndefined(columns[i][j])) {
                 throw new Error("Source data is missing a component at (" + i + "," + j + ")!");
             }
-            new_rows[j - 1][key] = columns[i][j];
+            newRows[j - 1][key] = columns[i][j];
         }
     }
-    return new_rows;
+
+    return newRows;
 };
+
 c3_chart_internal_fn.convertDataToTargets = function (data, appendXs) {
     var $$ = this, config = $$.config,
         ids = $$.d3.keys(data[0]).filter($$.isNotX, $$),