Top 20 Node js error list

Here’s a list of common errors and issues you might face when working with Node.js, along with explanations for each:

1. Syntax Errors

• SyntaxError: Unexpected token: Indicates a typo or missing/extra character, such as parentheses, brackets, or quotes.
• SyntaxError: Unexpected end of input: Occurs when a block of code or string is not closed properly.
• SyntaxError: Identifier 'x' has already been declared: This happens when a variable is declared multiple times in the same scope.

2. Module and Package Errors

• Error: Cannot find module 'module-name': Occurs when a module is not installed or the import path is incorrect. Ensure you run npm install module-name.
• Module not found error with relative path: Indicates an incorrect relative path for importing local files.
• Error: EACCES: permission denied: Permission issues when accessing or modifying a file. You might need to run the command with sudo or adjust permissions.

3. Runtime Errors

• TypeError: Cannot read property 'X' of undefined: Occurs when trying to access a property on undefined or null.
• ReferenceError: X is not defined: Indicates a variable is used before it’s declared or outside of its scope.
• RangeError: Maximum call stack size exceeded: Usually happens due to an infinite loop or recursive function without an exit condition.

4. Asynchronous and Promise Errors

• UnhandledPromiseRejectionWarning: Occurs when a promise is rejected but no .catch() block is provided to handle the error.
• Error: Callback was already called: This error arises when a callback function is called multiple times in asynchronous code.
• TimeoutError: When an operation takes longer than expected, often in network requests or database calls.

5. File System (fs) Errors

• Error: ENOENT: no such file or directory: Indicates that a file or directory being accessed does not exist.
• Error: EISDIR: illegal operation on a directory: Trying to perform a file-specific operation on a directory.
• Error: EMFILE: too many open files: When too many file descriptors are open, exceeding the system's limit.

6. Network Errors

• ECONNREFUSED: The connection to an external server was refused, typically when the server is down or the address is incorrect.
• ECONNRESET: The connection was forcibly closed by the remote host, possibly due to timeout or server restart.
• EADDRINUSE: The specified port is already in use by another process.

7. Event Loop and Blocking Code

• Error: Blocking the event loop: Occurs when synchronous code or heavy processing delays Node’s event loop, affecting performance.
• Warning: Possible EventEmitter memory leak detected: Triggered when more than 10 listeners are added to an EventEmitter, which might indicate a memory leak.

8. Database Connection Errors

• MongoNetworkError: Common in MongoDB connections, usually due to network issues or misconfiguration.
• SequelizeDatabaseError: An error in Sequelize, typically due to syntax issues in SQL queries or incorrect database connection configurations.
• Error: connect ETIMEDOUT: A connection to the database server timed out, often due to network issues or server unavailability.

9. Environment Variable Issues

• process.env returns undefined: Ensure environment variables are properly set in .env or passed during runtime.
• Error: Missing required environment variables: Happens when your code depends on an environment variable that is not defined.

10. npm and Package Management Issues

• npm ERR! code E404: Package not found in the registry, often due to incorrect package name or version.
• npm WARN deprecated: Warning about deprecated packages, suggesting they may not be maintained or have better alternatives.
• npm ERR! peer dep missing: Missing a peer dependency that a package requires.

11. Security and Vulnerability Warnings

• npm audit warnings: Indicate vulnerabilities in the installed packages, which can often be fixed with npm audit fix.
• Security warnings from packages: Generated by tools like npm audit or snyk, indicating potential security risks.

12. Memory and Performance Issues

• Error: JavaScript heap out of memory: Happens when Node.js runs out of memory, often due to handling large data sets or memory leaks.
• High CPU usage: Caused by blocking code or excessive synchronous processing in the Node.js event loop.

13. Middleware and Framework Errors (Express.js)

• Error: Cannot set headers after they are sent to the client: Occurs when res.send() or res.json() is called multiple times.
• TypeError: Router.use() requires a middleware function but got a 'X': Indicates that the use() method received an invalid argument (e.g., not a function).
• 404 Error for routes: Indicates that the specified route was not found; ensure route paths are correctly set up.

14. Logging and Debugging Issues

• Error logs missing context: Can happen if logging is not configured properly.
• Silent failures: Code fails without errors being thrown; often due to missing error-handling mechanisms.

15. Version and Compatibility Errors

• Error due to incompatible Node.js version: Ensure that the code or packages are compatible with your current Node.js version.
• ES module compatibility issues: Using import and export in projects that are not configured for ECMAScript modules. Ensure type: "module" is set in package.json.

16. Cross-Origin Resource Sharing (CORS) Errors

• CORS policy: No 'Access-Control-Allow-Origin' header is present: Configure CORS middleware in Express or another framework to handle cross-origin requests.
• Blocked by CORS policy: The server does not have the required CORS headers.

17. File Upload and Parsing Errors

• Error: Multipart: Boundary not found: Occurs during file uploads when the multipart boundary is missing or misconfigured.
• Error: Request body larger than maxBodyLength: The uploaded file exceeds the allowed request body size.

18. Token and Authentication Issues

• Error: Invalid token: Occurs when verifying a token that is malformed or expired.
• Error: jwt must be provided: Missing token in authorization headers or request.
• UnauthorizedError: No authorization token was found: Token required for protected routes is missing or invalid.

19. File Path Issues

• Path must be a string: Ensure that path variables passed to fs functions are correctly formatted.
• Incorrect file or folder path: Caused by incorrect use of relative paths in require or import statements.

20. Miscellaneous

• Error: spawn ENOENT: Indicates that the process cannot be spawned due to an incorrect command or missing executable.
• DeprecationWarnings: Warning about deprecated Node.js or package features that may be removed in future versions.
• Error: Assertion failed: Typically a logical error or failed condition check in code.

Debugging Tips:

• Use Node.js built-in debugging tools: Use node --inspect for Chrome DevTools debugging.
• Use proper error-handling mechanisms: Wrap asynchronous code in try/catch blocks and attach .catch() to promises.
• Log errors: Use proper logging libraries like winston or bunyan for better error visibility and tracking.

This list should help in identifying and resolving common Node.js errors effectively.