Babel giving Unexpted token while building

Question

I am trying to build my react library , and npm build gives this error . what is causing this error and how to fix it ?

    src/lib/CircularProfiles.js -> dist/CircularProfiles.js
    SyntaxError: src/lib/Github.js: Unexpected token (14:10)
      12 | class GithubProfileBar extends Component {
      13 |
    > 14 |     state = {
         |           ^
      15 |         totalRepos: 0,
      16 |         totalStars: 0,
      17 |     }

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] build: `rm -rf dist && NODE_ENV=production babel src/lib --out-dir dist --copy-files --ignore __tests__,spec.js,test.js,__snapshots__`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the [email protected] 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/natesh/.npm/_logs/2018-12-26T03_51_21_931Z-debug.log

My .babelrc file :

{
    "presets": [
        "es2015",
        "react"
    ]
}

Solution 1

I found that the error is because of older version of babel which doesn't handle newer versions of react code.

Here's the fix :

My problem was of older babel version fixed easily by installing:

npm i -D @babel/plugin-proposal-class-properties \
  @babel/preset-react \
  @babel/preset-env \
  @babel/core \
  @babel/plugin-transform-runtime \

In .babelrc file :

{
   "presets": [
       "@babel/react" , 
       "@babel/env" , 
   ],
   "plugins": [
       "@babel/plugin-proposal-class-properties"
   ]
}

Now babel built it successfully after this.

Solution 2

Make sure you are not using both v7 and v6 branch og babel. The "@babel/core" is the 7x branch and the "babel/core" is the 6x branch, you should not have both installed at once!