verify_uglifyjs_error

function verify_uglifyjs_error {
  # Create stub dependency
  echo "module.exports = class {}" >> packages/react-scripts/node_modules/es6-sample.js
  # Save App.js, we're going to modify it
  cp packages/react-scripts/template/src/App.js packages/react-scripts/template/src/App.js.bak

  # Add an es6 dependency
  echo "import es6 from 'es6-sample'" | cat - packages/react-scripts/template/src/App.js > packages/react-scripts/template/src/App.js.temp && mv packages/react-scripts/template/src/App.js.temp packages/react-scripts/template/src/App.js


  if `npm run build` | grep -xqFe "Failed to minify the code from this file: 

 ./packages/react-scripts/~/es6-sample.js line 1:0 

Read more here: http://bit.ly/2tRViJ9" 
  then
    echo "matched"
  else
    echo "not matched"
  fi
  # Restore App.js
  rm packages/react-scripts/template/src/App.js
  mv packages/react-scripts/template/src/App.js.bak packages/react-scripts/template/src/App.js
}