Understanding and Fixing the "Uncaught SyntaxError: Unexpected token export" in JavaScript

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It seems you’ve hit the “Uncaught SyntaxError: Unexpected token export” error, Isn’t it? No worries, Let’s break down why it’s throwing a fit and I’ll guide you through some fixes. We’ll get you back up and running in no time!

Table of Contents

1 What Causes This Error?
2 Steps to replicate the issue
3 How to Fix the Error
4 Other Common Troubleshooting Steps/Fixes
5 Conclusion

What Causes This Error?

The error message “Uncaught SyntaxError: Unexpected token export” is typically thrown by the JavaScript engine when it encounters an export statement unexpectedly. This situation can arise due to several reasons:

1. Incorrect Placement of Export Statement

The export statement allows modules to export functions, objects, or primitive values so that they can be used by other modules with the import statement. If an export the statement is placed outside a module context, the JavaScript engine will not recognize it, leading to this syntax error.

Example of Incorrect Usage:

// Assuming this script is not a module
export const myFunction = () => {
  console.log('Hello, Learners!');
};

2. Lack of Module System Support

If your JavaScript environment or the browser does not support ES6 modules, or if the script tag does not include the type="module" attribute, using export can cause this error. For browsers, ES6 modules need to be explicitly declared using <script type="module" src="..."></script> HTML.

Example of Correct Declaration:

<script type="module" src="myModule.js"></script>

3. Babel/Transpiler Configuration Issues

Many projects use JavaScript transpilers like Babel to convert ES6+ code to a version compatible with older browsers. An incorrect or missing configuration for these tools might prevent export statements from being properly transpiled.

4. Incorrect MIME Type

Modules must be served with the correct MIME type, which is application/javascript. If the server sends the files with an incorrect MIME type, the module features, including export, will not be recognized by the browser.

Steps to replicate the issue

To replicate the “Uncaught SyntaxError: Unexpected token export” error, we need to intentionally create a situation where the export the statement is used incorrectly.

Step 1: Create a JavaScript File with an Export Statement

// Create file named "incorrectModule.js" with below content
export const myFunction = () => {
  console.log('This will not work if not treated as a module.');
};

Step 2: Create an HTML File that Imports the Script Incorrectly

Next, create an HTML file named index.html and include the incorrectModule.js script without specifying type="module" in the <script> tag. This mimics the incorrect usage scenario.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Incorrect Module Example</title>
</head>
<body>
    <script src="incorrectModule.js"></script>
</body>
</html>

Step 3: Serve the HTML File

For testing, We can use the “SimpleHTTPServer“, This will help to host the index.xml and can be accessed via browser locally

Python 3.x:

python -m http.server

Python 2.x:

python -m SimpleHTTPServer

NOTE: Make sure you have both index.html and incorrectModule.js are available in the same path.

python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ...
10.19.28.123 - - [27/Feb/2024 18:20:39] "GET / HTTP/1.1" 200 -
10.19.28.123 - - [27/Feb/2024 18:20:39] "GET /incorrectModule.js HTTP/1.1" 200 -

Output: To view the error, Go to -> Brower -> Options -> More tools -> developer tools -> console [Google Chrome]

Relicate the error "Unexpected token export"

How to Fix the Error

Resolving the Uncaught SyntaxError: Unexpected token export error involves addressing the root cause. Here are practical steps to fix the issue:

Resolve the above-simulated ERROR

Let’s start with resolving the simulated error that we discussed above. This requires specifying type="module" in the <script> tag that includes the JavaScript file.

Replace the line

<script src="incorrectModule.js"></script>

with

<script type="module" src="incorrectModule.js"></script>

on the file index.xml

This should resolve the issue

Other Common Troubleshooting Steps/Fixes

Check JavaScript Environment Support

Verify that your JavaScript environment supports ES6 modules. Modern browsers support modules, but if you’re running scripts in a non-browser environment or an older browser, you might encounter compatibility issues.

Configure Babel/Transpiler Properly

If you’re using a transpiler, ensure it’s configured correctly to handle ES6 modules. This typically involves setting up a .babelrc file or similar configuration file with the appropriate plugins and presets.

Verify Server Configuration

Ensure your server is set up to serve JavaScript files with the application/javascript MIME type. This configuration varies depending on the server software (Apache, Nginx, etc.), so consult the relevant documentation.

Conclusion

By understanding the causes and implementing the solutions outlined above, we can able to understand and resolve the error “Uncaught SyntaxError: Unexpected token export“. Remember, the key to resolving such issues lies in adhering to modern JavaScript standards and ensuring that your development and deployment environments are properly configured.

Happy Learning!!

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Jerry Richard

Cloud Premier Engineer at Cloudera

Jerry grew up in a small town where he enjoyed playing video games. Once out of the nest, he pursued a Bachelor's degree in Computer Engineering. After college, he ultimately landed in the IT industry. Currently, he has over 10 years of experience. In his spare time, Jerry enjoys spending time with his family.

He is creator of this website - unexpectedendoffile.com, A website dedicated to share the mistake and experience learned.