import express from 'express'; SyntaxError: Unexpected identifier [duplicate]

Question

I don't understand what is wrong. Node v5.6.0 NPM v3.10.6

The code:

function (exports, require, module, __filename, __dirname) {
    import express from 'express'
};

The error:

SyntaxError: Unexpected token import
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:387:25)
    at Object.Module._extensions..js (module.js:422:10)
    at Module.load (module.js:357:32)
    at Function.Module._load (module.js:314:12)
    at Function.Module.runMain (module.js:447:10)
    at startup (node.js:140:18)
    at node.js:1001:3

Answer 1

Node 13+ Since Node 13, you can use either the .mjs extension, or set {"type": "module"} in your package.json. You don't need to use the --experimental-modules flag. Modules is now marked as stable in node.js

Node 12 Since Node 12, you can use either the .mjs extension, or set "type": "module" in your package.json. And you need to run node with the --experimental-modules flag.

Node 9 In Node 9, it is enabled behind a flag, and uses the .mjs extension.

node --experimental-modules my-app.mjs

---

While import is indeed part of ES6, it is unfortunately not yet supported in NodeJS by default, and has only very recently landed support in browsers.

See browser compat table on MDN and this Node issue.

From James M Snell's Update on ES6 Modules in Node.js (February 2017):

Work is in progress but it is going to take some time — We’re currently looking at around a year at least.

Until support shows up natively (now marked stable in Node 13+), you'll have to continue using classic require statements:

const express = require("express");

If you really want to use new ES6/7 features in NodeJS, you can compile it using Babel. Here's an example server.

Answer 2

Unfortunately, Node.js doesn't support ES6's import yet.

To accomplish what you're trying to do (import the Express module), this code should suffice

var express = require("express");

Also, be sure you have Express installed by running

$ npm install express

See the Node.js Docs for more information about learning Node.js.

Answer 3

I'm shocked esm hasn't been mentioned. This small, but mighty package allows you to use either import or require.

Install esm in your project

$ npm install --save esm

Update your Node Start Script to use esm

node -r esm app.js

esm just works. I wasted a TON of time with .mjs and --experimental-modules only to find out a .mjs file cannot import a file that uses require or module.exports. This was a huge problem, whereas esm allows you to mix and match and it just figures it out... esm just works.

Answer 4

As mentioned in other answers Node JS currently doesn't support ES6 imports.

(As of now, read EDIT 2)

Enable ES6 imports in node js provides a solution to this issue. I have tried this and it worked for me.

Run the command:

    npm install babel-register babel-preset-env --save-dev

Now you need to create a new file (config.js) and add the following code to it.

    require('babel-register')({
        presets: [ 'env' ]
    })
    // Import the rest of our application.
    module.exports = require('./your_server_file.js')

Now you can write import statements without getting any errors.

Hope this helps.

EDIT:

You need to run the new file which you created with above code. In my case it was config.js. So I have to run:

    node config.js

EDIT 2:

While experimenting, I found one easy solution to this issue.

Create .babelrc file in the root of your project.

Add following (and any other babel presets you need, can be added in this file):

    {
        "presets": ["env"]
    }

Install babel-preset-env using command npm install babel-preset-env --save, and then install babel-cli using command npm install babel-cli -g --save

Now, go to the folder where your server or index file exists and run using: babel-node fileName.js

Or you can run using npm start by adding following code to your package.json file:

    "scripts": {
        "start": "babel-node src/index.js"
    }