use object.assign pollfill

to support ES5 environments eg IE11

package.json

@@ -83,6 +83,7 @@
     "sinon": "^1.17.7"
   },
   "dependencies": {
-    "deep-diff": "^0.3.5"
+    "deep-diff": "^0.3.5",
+    "object.assign": "^4.0.4"
   }
 }

spec/diff.spec.js

@@ -1,6 +1,7 @@
 import sinon from 'sinon';
 import { expect } from 'chai';
 import { style, render, default as diffLogger } from '../src/diff';
+import { merge } from '../src/helpers';
 
 context('Diff', () => {
   describe('style', () => {
@@ -90,7 +91,7 @@ context('Diff', () => {
     });
 
     it('should log no diff without group', () => {
-      const loggerWithNoGroupCollapsed = Object.assign({}, logger, {
+      const loggerWithNoGroupCollapsed = merge(logger, {
         groupCollapsed: () => {
           throw new Error()
         },

src/helpers.js

@@ -1,9 +1,13 @@
+import objectAssign from 'object.assign';
+
 export const repeat = (str, times) => (new Array(times + 1)).join(str);
 
 export const pad = (num, maxLength) => repeat('0', maxLength - num.toString().length) + num;
 
 export const formatTime = time => `${pad(time.getHours(), 2)}:${pad(time.getMinutes(), 2)}:${pad(time.getSeconds(), 2)}.${pad(time.getMilliseconds(), 3)}`;
 
+export const merge = (...args) => objectAssign({}, ...args);
+
 // Use performance API if it's available in order to get better precision
 export const timer =
 (typeof performance !== 'undefined' && performance !== null) && typeof performance.now === 'function' ?

src/index.js

@@ -1,5 +1,5 @@
 import printBuffer from './core';
-import { timer } from './helpers';
+import { timer, merge } from './helpers';
 import defaults from './defaults';
 /* eslint max-len: ["error", 110, { "ignoreComments": true }] */
 /**
@@ -22,7 +22,7 @@ import defaults from './defaults';
  * @returns {function} logger middleware
  */
 function createLogger(options = {}) {
-  const loggerOptions = Object.assign({}, defaults, options);
+  const loggerOptions = merge(defaults, options);
 
   const {
     logger,
@@ -97,7 +97,7 @@ const store = createStore(
       ? diffPredicate(getState, action)
       : loggerOptions.diff;
 
-    printBuffer(logBuffer, Object.assign({}, loggerOptions, { diff }));
+    printBuffer(logBuffer, merge(loggerOptions, { diff }));
     logBuffer.length = 0;
 
     if (logEntry.error) throw logEntry.error;