JavaScript — How to Fix “Uncaught SyntaxError: Cannot use import statement outside a module”

JavaScript programs started small by being used here and there. Over time, the usage of JavaScript increased and we’re writing full applications that run in the browser. These large applications can be hard to maintain. It makes sense to think about ways of splitting them up into modules.

Modern browsers ship with native module support allowing them to optimize which module must be loaded.

A common error with modules is the “Uncaught SyntaxError: Cannot use import statement outside a module”. This error means you must explicitly tell the environment that the loaded file is a module. Let’s have a look at how to do that in the browser and Node.js

Node.js Series Overview

  1. String Replace All Appearances
  2. Remove All Whitespace From a String in JavaScript
  3. Generate a Random ID or String in Node.js or JavaScript
  4. Remove Extra Spaces From a String in JavaScript or Node.js
  5. Remove Numbers From a String in JavaScript or Node.js
  6. Get the Part Before a Character in a String in JavaScript or Node.js
  7. Get the Part After a Character in a String in JavaScript or Node.js
  8. How to Check if a Value is a String in JavaScript or Node.js
  9. Check If a String Includes All Strings in JavaScript/Node.js/TypeScript
  10. Check if a Value is a String in JavaScript and Node.js
  11. Limit and Truncate a String to a Given Length in JavaScript and Node.js
  12. Split a String into a List of Characters in JavaScript and Node.js
  13. How to Generage a UUID in Node.js
  14. Reverse a String in JavaScript or Node.js
  15. Split a String into a List of Lines in JavaScript or Node.js
  16. Split a String into a List of Words in JavaScript or Node.js
  17. Detect if a String is in camelCase Format in Javascript or Node.js
  18. Check If a String Is in Lowercase in JavaScript or Node.js
  19. Check If a String is in Uppercase in JavaScript or Node.js
  20. Get the Part After First Occurrence in a String in JavaScript or Node.js
  21. Get the Part Before First Occurrence in a String in JavaScript or Node.js
  22. Get the Part Before Last Occurrence in a String in JavaScript or Node.js
  23. Get the Part After Last Occurrence in a String in JavaScript or Node.js
  24. How to Count Words in a File
  25. How to Shuffle the Characters of a String in JavaScript or Node.js
  26. Append Characters or Words to a String in JavaScript or Node.js
  27. Check if a String is Empty in JavaScript or Node.js
  28. Ensure a String Ends with a Given Character in JavaScript or Node.js
  29. Left-Trim Characters Off a String in JavaScript or Node.js
  30. Right-Trim Characters Off a String in JavaScript or Node.js
  31. Lowercase the First Character of a String in JavaScript or Node.js
  32. Uppercase the First Character of a String in JavaScript or Node.js
  33. Prepend Characters or Words to a String in JavaScript or Node.js
  34. Check if a String is a Number
  35. Convert a String to Buffer

Fix “Uncaught SyntaxError” in the Browser

Browsers support modules out of the box. But you must tell the browser that imports using a <script> tag should be handled as a module. For example, frontend tools like Vite create a modern output bundle using modules.

Fix the syntax error by adding type="module" to your script tags:

<script type="module" src="/assets/app.js"></script>  

Fix “Uncaught SyntaxError” in Node.js

You must tell Node.js that you’re using modules when your code is using import or export keywords. Node.js in version 18.x uses CommonJS as the default, but CommonJS doesn’t support these keywords. You must run your app as a module. You can do that by setting the type: "module" of your app inside the package.json file:

package.json

{
  "type": "module"
}

This resolves the “Uncaught SyntaxError” in your Node.js application and you can write modern code using ECMAScript modules.

Enjoy!


Mentioned Resources

Explore the Library

Find interesting tutorials and solutions for your problems.