[Must-Read for Beginners] Key Points to Check and Tips for Solving Errors in Node.js

Who Is This Information For?

This article is aimed at beginner to intermediate engineers who are developing web applications or backend processes using Node.js.
It will serve as a reliable guide for those who feel, “I encountered an error, but I don’t know where to look,” or “I searched online but still can’t figure it out.”
It’s also helpful for those assigned to troubleshoot in team projects or freelancers who want to strengthen their self-resolution skills.

First Things First: Basic Structure of Node.js Errors

When an error occurs in Node.js, a stack trace (error message) is displayed in the terminal.
This contains valuable clues such as the type of error, location of occurrence, and call stack history.

A typical error message structure looks like this:

TypeError: Cannot read property 'name' of undefined
    at Object.<anonymous> (/path/to/project/app.js:10:15)
    at Module._compile (node:internal/modules/cjs/loader:1103:14)
    ...

Rather than just skimming through such logs, you should learn the skill of reading and interpreting them.

Step ①: Identify the Type of Error

Node.js errors can generally be categorized as follows:

• SyntaxError
  → Mistakes in code structure (e.g., missing commas, unclosed brackets)

• ReferenceError
  → Using undefined variables or functions

• TypeError
  → Trying to access a method on undefined or null

• RangeError
  → Array index out of range, etc.

• Error (General Exception)
  → Custom-thrown errors or those occurring within modules

The error type always appears at the beginning of the log. Identifying the name is your first step.

Step ②: Master Stack Trace Reading

The location where the error occurred is shown in the stack trace. Here are three key points to check:

1. Check the file name and line number
   → Clearly indicated like /app.js:10:15.

2. Check where the error was called from
   → The function name or module helps trace the logic flow.

3. Determine if the error is from external modules or your own code
   → Errors inside node_modules/ may originate from library issues.

Sample:

TypeError: Cannot read properties of undefined (reading 'title')
    at renderTitle (/project/controllers/book.js:22:11)
    at getBookDetail (/project/controllers/book.js:10:3)

→ It’s clear that renderTitle is trying to access undefined.title.

Step ③: Common Errors and How to Fix Them

■ “Cannot read properties of undefined” Error

Possible Causes:

• Trying to access a property on an undefined object
• Using an asynchronous return value without checking it

Solutions:

• Use console.log() to check if the variable has a value
• Add guard clauses like obj?.property or if (!obj)

■ “Module not found” Error

Possible Causes:

• Incorrect file path in require() or import
• Module not installed

Solutions:

• Check the difference between relative and absolute paths
• Run npm install again or check dependencies in package.json

■ “UnhandledPromiseRejectionWarning” Error

Possible Causes:

• Missing .catch on a Promise or lack of try-catch for async/await

Solutions:

• Always include error handling in asynchronous processes:

try {
  await fetchData();
} catch (err) {
  console.error(err);
}

Step ④: Use Debugging Tools Effectively

Debugging tools such as Node.js debugger and breakpoints in VS Code can be extremely helpful.

• Run step-by-step using node inspect app.js
• Use debugger keyword to pause at specific points
• Don’t rely solely on console.log() — stack traces are key to deeper insight

Also, using the --trace-warnings option highlights deprecated API warnings clearly.

Step ⑤: When You Still Can’t Solve It

• Copy the full error message and search it (in English)
• Check GitHub Issues, Stack Overflow, Qiita for similar cases
• Include the module name and version in your search
• Reproduce the issue with a minimal code snippet to isolate the problem

※ For complex projects, rebuilding from a minimal setup can be an effective strategy.

Accessibility Considerations

This content is designed with readability and understanding in mind for all audiences:

• Balanced use of technical and simple language: Avoids jargon overload while maintaining accuracy.
• Clear separation of sections and headings: Reduces cognitive load and supports screen reader users.
• Concrete code examples: Enhances visual and logical understanding.
• Step-by-step structure: Organizes information progressively for beginner-friendly learning.

We believe true accessibility lies in “ease of understanding,” and aim to provide that through simple yet thorough explanations.

Summary: Become Stronger at Handling Node.js Errors

• When an error appears, the first step is to calmly read the message.
• Analyze the “error type,” “location,” and “stack trace” as a set.
• Most common errors follow familiar patterns — knowing these structures helps you respond calmly.
• With proper debugging methods and search skills, error handling becomes much less stressful.

How you handle errors is where you show your true developer skills.
Keep building experience, and get more comfortable working with Node.js!