Fix entrypoints compatibility for older Node versions (#194)

* Fix `entrypoints` compatibility for older Node versions

* Use `object.entries` package

Author: samuelmeuli

lib/plugin.js

@@ -1,3 +1,4 @@
+var entries = require('object.entries');
 var path = require('path');
 var fse = require('fs-extra');
 var _ = require('lodash');
@@ -166,12 +167,12 @@ ManifestPlugin.prototype.apply = function(compiler) {
           // Webpack 4+
           compilation.entrypoints.entries() :
           // Webpack 3
-          Object.entries(compilation.entrypoints)
+          entries(compilation.entrypoints)
+      );
+      const entrypoints = entrypointsArray.reduce(
+        (e, [name, entrypoint]) => Object.assign(e, { [name]: entrypoint.getFiles() }),
+        {}
       );
-      const entrypoints = entrypointsArray.reduce((e, [name, entrypoint]) => ({
-        ...e,
-        [name]: entrypoint.getFiles()
-      }), {});
       manifest = this.opts.generate(seed, files, entrypoints);
     } else {
       manifest = files.reduce(function (manifest, file) {

package.json

@@ -43,6 +43,7 @@
   "dependencies": {
     "fs-extra": "^7.0.0",
     "lodash": ">=3.5 <5",
+    "object.entries": "^1.1.0",
     "tapable": "^1.0.0"
   },
   "jest": {

spec/plugin.spec.js

@@ -756,10 +756,10 @@ describe('ManifestPlugin', function() {
     {
       manifestOptions: {
         generate: (seed, files, entrypoints) => {
-          const manifestFiles = files.reduce((manifest, { name, path }) => ({
-            ...manifest,
-            [name]: path
-          }), seed);
+          const manifestFiles = files.reduce(
+            (manifest, { name, path }) => Object.assign(manifest, { [name]: path }),
+            seed
+          );
           return {
             files: manifestFiles,
             entrypoints