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npm run build: fails in node_module on "class" or prototype defination

See original GitHub issue

Is this a bug report?

Not sure

Can you also reproduce the problem with npm 4.x?


Which terms did you search for in User Guide?

deploy configure


  1. node -v: v8.2.1
  2. npm -v: 5.3.0
  3. yarn --version (if you use Yarn):
  4. npm ls react-scripts (if you haven’t ejected): react-scripts@1.0.12

Then, specify:

  1. Operating system: ubuntu 16.04
  2. Browser and version (if relevant):

Steps to Reproduce

(Write your steps here:)

  1. npm i eosjs-ecc
  2. require(‘eosjs-ecc’)
  3. npm run build

Expected Behavior


Actual Behavior

npm run build

> react-scripts build

Creating an optimized production build...
Failed to compile.

Failed to minify the code from this file: 


Read more here:

npm ERR! errno 1
npm ERR! keygen@0.1.0 build: `react-scripts build`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the keygen@0.1.0 build script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/.npm/_logs/2017-09-01T17_29_14_675Z-debug.log

Line 25 is either “class” in or in my local testing the first nonoccurence of “ =”

Reproducible Demo

none yet

Prototype and classes are pretty standard I’m not sure why this would fail…

Issue Analytics

  • State:closed
  • Created 6 years ago
  • Comments:13 (8 by maintainers)

github_iconTop GitHub Comments

Timercommented, Sep 18, 2017

@jcalfee ah, that’s where our misunderstanding is!

We do not compile any code from node_modules, so it stays as-is. Even if we were to convert to Uglify v3, uses of class would leak into code targeting IE 9 since it could be parsed then, but then bomb out the browser.

We do not compile node_modules because it’s incredibly slow and tends to break packages.

jcalfeecommented, Sep 18, 2017

Your concern is about the build output code version. But this issue is about the version of the dependent modules going into the build… These should be two different things.

How about run the babel es2015 conversion before Uglify v2? This is the code I used in my module to make it comparable with create-react-app. If create-react-app did this then many other modules would be spared from having to generate and deploy the generated copy to npm (which is a challenge to keep in sync).I think this is reasonable since old browsers do not run code directly from npm, they always go though a build process.

The trick is to create the more compatible generated code as late as possible.

node_modules/babel-cli/bin/babel.js src --out-dir lib


"babel": {
    "presets": [
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