How I Fixed: UglifyJs Unexpected token: name (DropIn)

I’ve been trying – in vain – to build the front end for CodeReviewVideos. The issue I have been hitting upon is as follows:

ERROR in app.a2e9a6b7afa471d94d2b.js from UglifyJs
Unexpected token: name (DropIn) [./node_modules/braintree-web-drop-in-react/dist/index.js:109,0][app.a2e9a6b7afa471d94d2b.js:116396,6]


As the error states, the issue is with the UglifyJs plugin, which I use in combination with WebPack.

This is a frustrating show-stopping problem. Unless fixed, I couldn’t complete a build.

Here’s what I had in my WebPack prod config:

      new webpack.optimize.UglifyJsPlugin({
        beautify: false,
        mangle: {
          screw_ie8: true,
          keep_fnames: true
        compress: {
          screw_ie8: true,
          warnings: false
        comments: false

This was only in my WebPack prod config. Therefore I didn’t notice any issue until trying to build for prod.

Now, in truth, I didn’t write the code / config above. I copy / pasted from somewhere else (I forget where) and as it just worked I didn’t pay much attention to it.

When it stopped working, I got sad, then got on to trying to fix it.

My Solution

There’s a bunch of suggested general solutions to this problem. A quick Google will turn up plenty of GitHub issues. Unfortunately none of them were specific to my exact error.

In my case, as best I understand it, the Braintree Web Drop In React should have compiled the dist.js file down to ES5, but is instead, in ES6. I concluded this based on this and this.

Dammit Jim, I’m a coder not a WebPack genius

Of course, I may be wrong.

Fixing this wasn’t that hard. I just needed to read the docs.

yarn add --dev uglifyjs-webpack-plugin

For me, this added:

"uglifyjs-webpack-plugin": "^1.2.4",

To my devDependencies in package.json.

After which I updated my prod.js WebPack config as follows:

"use strict";

const webpack = require("webpack");
const UglifyJsPlugin = require('uglifyjs-webpack-plugin');

module.exports = function() {
  console.log("BUILDING PRODUCTION");

  return webpackMerge(commonConfig(), {

    plugins: [

      new UglifyJsPlugin({
        test: /\.js($|\?)/i,
        sourceMap: true,
        uglifyOptions: {
          mangle: {
            keep_fnames: true,
          compress: {
            warnings: false,
          output: {
            beautify: false,


I’ve removed everything unrelated to this specific problem.

After which I could get my build to work.

Published by

Code Review

CodeReviewVideos is a video training site helping software developers learn Symfony faster and easier.

11 thoughts on “How I Fixed: UglifyJs Unexpected token: name (DropIn)”

  1. please could you share your package file or your project , I have problem with webpackMerge function

    “ReferenceError: webpackMerge is not defined”
    what is your version the webpack?

  2. I need to find you buy you a beer!
    Your code just save me tons of headaches!
    I friggin love you right now man, Thanks alot!

  3. I was almost a week trying to solve this problem, I was on the edge of despair, this was the only one that It worked. I thank you for sharing this article.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.