Unexpected reserved word 'import' when using babel

Question

Using Babel in my NodeJSv4.1.1 code.

Got the require hook in:

require("babel-core/register");

$appRoot = __dirname;

module.exports = require("./lib/controllers/app");

In a subsequently lodaded .js file I am doing:

import { Strategy as LocalStrategy } from "passport-local";

However this is generating the following error in the CLI:

import { Strategy as LocalStrategy } from "passport-local";
^^^^^^

SyntaxError: Unexpected reserved word
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:413:25)
    at loader (/Users/*/Documents/Web/*/node_modules/babel-core/node_modules/babel-register/lib/node.js:128:5)
    at Object.require.extensions.(anonymous function) [as .js] (/Users/*/Documents/Web/*/node_modules/babel-core/node_modules/babel-register/lib/node.js:138:7)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Module.require (module.js:365:17)
    at require (module.js:384:17)
    at module.exports (index.js:9:5)
    at Object.<anonymous> (app.js:102:39)

Solution 1

Sounds like you aren't using the right presets. As of babel 6, the core babel loader no longer includes the expected ES6 transforms by default (it's now a generic code transformer platform), instead you must use a preset:

require('babel-register')({
        "presets": ["es2015"]
});

You will also need to install the preset package:

npm install --save-dev babel-preset-es2015

Solution 2

It seems that this file is not being transpiled. Is this subsequently loaded .js file in the node_modules directory? If so, you need to:

require("babel-core/register")({
  // This will override `node_modules` ignoring - you can alternatively pass
  // an array of strings to be explicitly matched or a regex / glob
  ignore: false
});

By default all requires to node_modules will be ignored. You can override this by passing an ignore regex

https://babeljs.io/docs/usage/require/

Comments

[max]

what version of Babel?

[rcjsdev]

"babel-core": "^6.1.21"

[max]

have you included any Babel plugins or presets?

[rcjsdev]

nope, i tried es2015preset but this broke my app as well, i got an issue where it was saying the following was undefined: $passport = require('passport');

[w00t]

Is this on line 1? The error is being reported by the babel module.

[Felix Kling]

Please read the tag descriptions. babel is for questions for a Python library with said name.

[max]

@Rob with the es2015 preset, if you change $passport = require('passport'); to var $passport = require('passport');, do you still see that error?

[ian]

This is a common error when running plain Node, which means you're likely seeing this because Babel isn't actually running. I would recommend switching over the the babel-register module as suggested by the docs since you're using Babel 6. Then make sure the file in question isn't getting ignored. See @pherris' comment below

[Jayesh]

Also make sure you have correct .babelrc. That was the problem in my case.

[Jules]

@ian - the stack dump includes this line: at loader (/Users/*/Documents/Web/*/node_modules/babel-core/node_modul‌​es/babel-register/li‌​b/node.js:128:5) which sure sounds like babel-register is being used to me...

[rcjsdev]

I have subsequent requires which the require other things does this work okay w/ babel?

[Admin]

where does this code belong? in a webpack config? in a babelconfig? in the code that I'm running?

[Arkadiy Kukarkin]

@omouse you'd usually put this into whatever your main entrypoint is, typically index.js at the top level, before requiring the rest of your code

[ArtHare]

As a little addition, I had to npm install --save-dev babel-preset-es2015 since it didn't come by default with babel-register. But this answer worked for me!

[Fractalf]

I tried all that is mentioned here, but still I get this error. Very annoying. I got the top require("babel-core/register"); upgraded node/npm to 4.4/3.8.1. Have a file .babelrc with { "presets": ["es2015"] }. Installed babel-core, babel-register, babel-preset-2015. My node file has just the require above and import asap from "asap"; right under...

[Arkadiy Kukarkin]

@Fractalf: the transpiler from babel-register does not apply to the file in which it is required, so you cannot use import in the same file. You must instead require another file which can then use full es2015 semantics

[Fractalf]

@ArkadiyKukarkin: thanks, so I tried to just require the es6 module and use babel-core in only that module, but then there is the same error just complaining about export. I got it all working with babel-node, and then just building it, but man how hard is this for a first time user! Very bad documentation for those who didn't touch babel yet :(

[Fractalf]

Finally found something that made this work: leanpub.com/setting-up-es6/read#sec_nodejs-babel-dynamic github.com/rauschma/node-babel-dynamic-demo

[yussan]

it's working after i place on very top of line on my app file root, thanks

[JREAM]

use babel-preset-env it covers babel-preset-2015-17 and its going to recommend it.

[2080]

I created a .babelrc in the root directory of the project and added { "presets": ["es2015"] } to it