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Fix "Export is Reserved" Error

By Filip on 04/18/2024

Troubleshoot the "Parsing error: The keyword 'export' is reserved" error and learn how to fix it with our comprehensive guide.

Fix "Export is Reserved" Error

Table of Contents

Introduction

This guide will help you fix the "Parsing error: The keyword '...' is reserved" error in JavaScript. This error usually happens when you use new JavaScript features without setting up your environment correctly.

Step-by-Step Solution

This error typically arises when using modern JavaScript features (like import or export) without configuring your environment to understand them. Here's how to tackle it:

1. Identify the problematic keyword:

The error message will specify the keyword causing the issue, such as import, export, or const. This helps pinpoint the area needing adjustment.

2. Check your environment:

  • ESLint:
    • parserOptions: Ensure your ESLint configuration file (.eslintrc) has the parserOptions field set correctly.
    • sourceType: Set "sourceType": "module" to enable ES modules and the use of import and export.
    • ecmaVersion: Specify the ECMAScript version you're using (e.g., 2020 for ES2020 features).
// .eslintrc example
{
  "parserOptions": {
    "sourceType": "module",
    "ecmaVersion": 2020
  }
}
  • TypeScript:
    • If using TypeScript with ESLint, ensure you have the @typescript-eslint/parser installed and configured as your parser.

3. Consider your JavaScript runtime:

  • Older browsers or environments might not support newer JavaScript features natively. You might need to transpile your code using tools like Babel to ensure compatibility.

4. Additional Tips:

  • Editor/IDE Configuration: Some editors have built-in linters that might need similar configuration adjustments as ESLint.
  • Build Tools: If you're using build tools like Webpack or Rollup, ensure they are configured to handle modern JavaScript features.

Example Scenario:

Let's say you encounter the error "Parsing error: The keyword 'import' is reserved" while using import statements in your JavaScript file.

  1. Identify: The problematic keyword is import.
  2. Check ESLint: Ensure your .eslintrc file has "sourceType": "module" set within parserOptions.
  3. Consider Runtime: If targeting older environments, use Babel to transpile your code.

By following these steps and understanding the root cause, you can effectively resolve parsing errors related to reserved keywords and leverage modern JavaScript features in your projects.

Code Example

This code explains how to fix the "Parsing error: The keyword '...' is reserved" error, which happens when using the 'import' keyword in environments that don't support ES modules. The example shows how to use Babel to transpile the code to be compatible with older environments.

This example demonstrates a scenario where the error occurs due to using the import keyword without proper configuration, and how to fix it using Babel.

Scenario:

You have a file named module.js with the following code:

// module.js
export const message = "Hello from the module!";

And another file named app.js attempting to import it:

// app.js
import { message } from './module.js';

console.log(message);

Running app.js in an older environment that doesn't support ES modules natively will result in the error: "Parsing error: The keyword 'import' is reserved".

Solution using Babel:

  1. Install Babel:
npm install --save-dev @babel/core @babel/cli @babel/preset-env
  1. Create a Babel configuration file (.babelrc):
{
  "presets": ["@babel/preset-env"]
}
  1. Transpile your code:
npx babel app.js -o compiled.js

This will create a new file compiled.js with the code transformed to be compatible with older environments.

compiled.js:

"use strict";

var _module = require("./module.js");

console.log(_module.message);

Now, running compiled.js should work without the parsing error.

Additional Notes:

  • This example focuses on the import keyword, but the same principles apply to other reserved keywords like export or features introduced in newer ECMAScript versions.
  • Adjust the Babel configuration based on your target environment and desired level of compatibility.
  • For larger projects, integrate Babel into your build process using tools like Webpack or Rollup.

Additional Notes

Understanding the Error:

  • This error indicates a mismatch between the JavaScript features you're using and the environment's ability to interpret them. Essentially, the environment doesn't recognize the keyword as valid syntax.

Beyond ESLint:

  • Other Linters: Similar configuration adjustments might be needed for linters like JSHint or JSLint if you're using them.
  • Bundlers: Tools like Webpack or Parcel might require specific loaders or plugins to handle modern JavaScript or transpilation.

Transpilation Considerations:

  • Target Environments: Choose the appropriate Babel presets based on the browsers or environments you need to support.
  • Polyfills: For features with no direct equivalent in older JavaScript, you might need to include polyfills to provide the necessary functionality.

Debugging Tips:

  • Isolate the Issue: If the error occurs in a large codebase, try to isolate the problematic code section to narrow down the cause.
  • Check for Typos: Ensure the keyword is spelled correctly and used in the right context. A simple typo can lead to this error.
  • Console Logs: Use console logs or a debugger to inspect variables and execution flow to identify potential issues.

Staying Updated:

  • Keep your tools and environment configurations up-to-date to ensure compatibility with the latest JavaScript features and avoid potential conflicts.

Community Resources:

  • Stack Overflow, GitHub issues, and online forums can be valuable resources for finding solutions and troubleshooting specific scenarios related to this error.

Summary

Issue Solution
ESLint Set "sourceType": "module" and appropriate ecmaVersion in .eslintrc.
TypeScript Use @typescript-eslint/parser.
Old browsers Transpile code using Babel.
Editor/IDE Adjust linter settings.
Build tools Configure to handle modern JavaScript.

Conclusion

By addressing the environment's ability to understand modern JavaScript features, you can effectively resolve the "Parsing error: The keyword '...' is reserved" error and leverage the full potential of JavaScript in your projects. Remember to consider the specific keyword causing the issue, configure your linting and build tools appropriately, and account for target environment compatibility through transpilation or polyfills. With careful troubleshooting and a solid understanding of the underlying causes, you can overcome this error and continue building robust and modern JavaScript applications.

References

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