How to Fix SyntaxError: Unexpected token ‘export’ in JavaScript

SyntaxError: Unexpected token ‘export’ error typically occurs in JavaScript when trying to “use ES6 module syntax in an environment that does not support it.”

Common reasons and fixes for the error

Here are a few common reasons for this error and their solutions:

  1. Check browser support for ES6
  2. Node.js Environment
  3. Check the correct syntax – use the type=”module” attribute in HTML
  4. Misplaced Export Statement
  5. Ensure you are not mixing the CommonJS module with the export keyword
  6. For server-side JavaScript, verify the Node.js version supports ES6
  7. Using Reserved Keywords

Check browser support for ES6

The ES6 (ECMAScript 2015) features support is very good across all modern browsers.

Here’s a general overview of browser support:

  1. Google Chrome: Full ES6 support from version 58 onwards. Partial support started around version 51.
  2. Mozilla Firefox: Full ES6 support from version 54 onwards. Partial support began much earlier.
  3. Microsoft Edge: Full ES6 support started with the initial versions of Edge. Edge has since moved to the Chromium engine with full ES6 support.
  4. Apple Safari: Full ES6 support from version 10 onwards.
  5. Opera: Since Opera also moved to the Chromium engine, its ES6 support timeline is similar to Chrome’s.

Node.js Environment

Older versions of Node.js did not support ES6 module syntax. If you are using an older version of Node.js, consider updating to the latest version.

Alternatively, you can use the CommonJS module system (require and module.exports) instead of ES6 modules (import and export).

Check the correct syntax – use the type=”module” attribute in HTML

When using ES6 modules in a browser, ensure you use the correct script type. You should set the type attribute of the script tag to the module.

<script type="module" src="path/to/your/script.js"></script>

Here are some key points to remember when using the type=”module” attribute:

Default Behavior: Scripts with type=”module” are deferred by default. This means they don’t block the HTML parser and will execute after the HTML document has been completely parsed. This behavior is similar to using the defer attribute on traditional scripts.

Scope: Scripts with type=”module” have their top-level scope. This means variables declared with let or const in the top scope of the module will not pollute the global namespace.

Importing Modules: Inside a module script, you can import other modules using the ES6 import statement.

import { functionName } from './anotherModule.js';

Inline Modules: You can also have inline module scripts using the same type="module" attribute:

<script type="module">
  import { functionName } from './anotherModule.js';
  // Your inline module code here
</script>

Nomodule Attribute: If you want to provide a fallback for older browsers that don’t support ES6 modules, you can use the nomodule attribute on a script:

<!-- For modern browsers -->
<script type="module" src="path/to/your/module.js"></script>

<!-- For older browsers -->
<script nomodule src="path/to/your/fallback/script.js"></script>

Browsers that understand type=”module” will ignore scripts with the nomodule attribute, and those that don’t understand type=”module” will run the scripts with the nomodule attribute.

Misplaced Export Statement

Ensure that the export statement is at the top-level scope of your module and not inside a function, loop, or conditional.

Ensure you are not mixing the CommonJS module with the ‘export’ keyword

Mixing CommonJS (used primarily in Node.js) with ES6 module syntax can cause issues and confusion. Here’s a quick distinction between the two:

CommonJS (CJS):

  1. Used primarily in Node.js (before ES6 module support was introduced).
  2. Uses require() to import modules.
  3. Uses module.exports or exports to export functions, objects, or values.
// Importing a module
const myModule = require('./myModule');

// Exporting a module
module.exports = {
  myFunction: function() {
    // function code...
  }
};

ES6 Modules

  1. Used in modern JavaScript, both on the client side and in newer versions of Node.js.
  2. Uses import and export keywords.
// Importing a module
import { myFunction } from './myModule.mjs';

// Exporting a function from a module
export function myFunction() {
  // function code...
}

If you mix the two, you may encounter errors or unexpected behavior.

If you’re transitioning a project from CommonJS to ES6 modules or vice versa, it’s beneficial to do so systematically and test thoroughly to ensure everything is working as expected.

For server-side JavaScript, verify the Node.js version supports ES6

Node.js has had support for most ES6 (ES2015) features for a while, but the level of support has varied across versions.

If you’re running server-side JavaScript and want to verify whether your Node.js version supports ES6 features, you can take the following steps:

Upgrade Node.js

If your Node.js version does not support the ES6 features you need, and there’s no constraint preventing an upgrade, consider upgrading to a newer Node.js version. This will give you access to modern JavaScript features and bring performance improvements and security patches.

Consider Using a Transpiler

If you need to use ES6 features but are stuck with an older Node.js version, consider using a transpiler like Babel.

Babel allows you to write code using the latest ES6 (or even newer) features and then transpile it down to ES5 code that can run on older Node.js versions.

Comparing with Node.js ES6 Support

Once you know your Node.js version, you can check its support for ES6 features:

  1. Node.js v4: Introduced some ES6 support but was incomplete.
  2. Node.js v6: Had significant ES6 support, covering about 99% of the ES6 specification.
  3. Node.js v8 and above: These versions fully support ES6 features.

Consideration for NextJS similar errors – next-transpile-modules

If you try to import an ES6 module in a Next.js application (which by default uses CommonJS), you might encounter an error similar to the “Unexpected token ‘export'” issue.

To fix the error, the Next.js community has introduced plugins like next-transpile-modules. This plugin lets you transpile third-party modules in node_modules, making them compatible with your Next.js application.

Here are some considerations and steps to use next-transpile-modules:

Install the package:

npm install next-transpile-modules --save-dev

Update your next.config.js:

const withTM = require('next-transpile-modules')(['some-module', 'another-module']);

module.exports = withTM({
  // your Next.js config
});

Here, ‘some-module’ and ‘another-module’ are placeholders for the actual names of the modules you want to transpile.

Summary

  1. Unexpected token ‘export’ Error:

    • Occurs when trying to use ES6 module syntax in an unsupported environment.
    • Solutions include: updating Node.js, using a bundler/transpiler, ensuring correct script type (type="module"), not mixing module systems, and placing export at the top-level.
  2. ES6 Browser Support:
    • Modern browsers (Chrome 58+, Firefox 54+, Edge, Safari 10+, and Opera with Chromium engine) fully support ES6.
    • Internet Explorer has limited ES6 support.
    • Use type="module" in script tags for ES6 modules in browsers.
  3. CommonJS vs. ES6 Modules:
    • Avoid mixing CommonJS (require, module.exports) with ES6 (import, export) in the same file.
    • Choose one system for consistency.
  4. Next.js & Module Issues:
    • Mixing module systems can cause errors.
    • next-transpile-modules allows for transpiling third-party modules in Next.js to resolve compatibility issues.
  5. Server-Side JavaScript & ES6:

    • Node.js v8 and above have nearly complete ES6 support.
    • Check Node.js version with node -v.
    • For specific ES6 feature support per Node version, refer to Node.green.
    • Upgrade Node.js or use a transpiler (like Babel) if necessary.

That’s all!

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