ESLint: Parsing error: Unexpected token in Next.js: Causes and How to Fix

Common Causes of ESLint Parsing Error

• Incorrect JavaScript Syntax: One of the most frequent causes of ESLint parsing errors is a syntax error in the JavaScript code itself. This can include missing semicolons, unmatched brackets, or misplaced parentheses. For instance, a missing bracket can lead to:

  ```javascript
  const obj = {
  key: 'value'
  // Missing closing brace above
  ```

 

• JavaScript Language Features: When using newer language features such as optional chaining or nullish coalescing without proper configurations or support from ESLint, parsing errors can occur.

  ```javascript
  const value = obj?.property; // Optional chaining
  const result = value ?? 'default'; // Nullish coalescing
  ```

 

• ESLint Configuration Issues: The ESLint configuration might not be set up to understand the latest JavaScript features or the specific syntax used in your project. This is especially relevant if the `parserOptions` property in your ESLint config file is not properly set to accommodate the ECMAScript version you are using.

  ```json
  {
  "parserOptions": {
  "ecmaVersion": 2020
  }
  }
  ```

 

• Missing Babel or ESLint Plugins: Projects using advanced JavaScript syntax or React, like Next.js, might require specific Babel configurations or ESLint plugins (e.g., `babel-eslint`, `@babel/eslint-parser`) to correctly parse new syntax. Failure to include them can result in parsing errors.

  ```json
  {
  "parser": "@babel/eslint-parser"
  }
  ```

 

• Configuration Conflicts: Sometimes, multiple configurations or settings can conflict with one another, causing parsing errors. This is common when inheriting settings through shared configs that aren't compatible with each other or with your project.

 

• Unsupported ECMAScript Proposals: If you're using experimental or unsupported ECMAScript proposals, those features might not be understood by ESLint's current parser, resulting in syntax parsing errors.

 

• Usage of TypeScript without Proper Parsing Setup: If you're incorporating TypeScript in your Next.js project, not setting up ESLint to parse TypeScript files correctly can lead to unexpected token errors. This requires setting the `@typescript-eslint/parser` in your .eslintrc configuration.

  ```json
  {
  "parser": "@typescript-eslint/parser"
  }
  ```