Error Handling in JavaScript: try/catch statements, error objects, debugging

Making mistakes occasionally when writing JavaScript code is common. Errors are what happen when something goes wrong, and they can make your code behave strangely or even stop functioning altogether.

Understanding proper error management techniques is crucial for this reason. To prevent larger issues, this entails identifying errors and fixing them.

I’ll discuss the various kinds of errors you might run into while writing JavaScript code in this article. I’ll explain why it’s crucial to understand how to handle these errors properly.

Show you how to use try/catch clauses and error objects to handle errors as well. Give you some advice on how to debug JavaScript code effectively and list some typical mistakes you might run into.

Error Handling in JavaScript: try/catch statements, error objects, debugging

Table Of Content

  1. Error Handling Basics & Types of Errors in JavaScript
  2. try/catch Statements in JavaScript
  3. Error Objects & Custom Errors in JavaScript
  4. Debugging
  5. Best Practices for Error Handling in JavaScript
  6. Conclusion

1. Error Handling Basics & Types of Errors in JavaScript

Sometimes, when we run the written JavaScript code doesn’t work as we expected. These issues are called errors.

It happen because of different reasons, like wrong information, mistakes in the code, internet problems, and more.

In JavaScript there are 3 types of errors –

  1. Syntax errors
  2. Runtime errors
  3. Logical errors

Syntax errors

When coding in JavaScript, it’s important to follow certain rules that dictate the use of appropriate punctuation and brackets. Failing to do so can result in a pesky syntax error that’ll probably drive you nuts! Fortunately, these errors are easy to identify since they happen right as you’re writing your code. Common offenders include forgetting semi-colons, using incorrect brackets or supplying wrong information when calling functions.


function addNumbers(num1, num2) {
     return num1 + num2;
console.log(addNumbers(5, 10);

This will give the following error when run the code: 

Uncaught SyntaxError: missing ) after argument list

In the example, there is a missing closing parenthe­sis at the end of the console.log. This will cause a syntax error, and the code will not execute.

Runtime errors

Code execution can be full of surprises, and not the good kind. When you thought everything was going well, runtime errors pop up out of nowhere and stop everything in its tracks. These coding errors can happen for many different reasons, like not defining variables or using functions that don’t exist. Even worse, these annoying errors don’t happen in a certain way or at a certain time. Instead, they happen at random and can leave your program hanging by a thread!


var x = 10;
var y = x.toUpperCase();

This will give the following error when run the code: 

Uncaught TypeError: x.toUpperCase is not a function

In the example, we are trying to call toUpperCase() method on a number type variable, which is not a valid operation. This will cause a runtime error, and the code will stop executing.

Logical errors

Detecting logical errors in code can be challenging since they don’t always trigger an error message but still lead to unexpected results. Such errors creep up when the code doesn’t adhere to its intended logic or misses critical steps. For instance, a function designed to add two numbers may erroneously output their difference instead, causing incorrect calculations.

Errors left unhandled can create havoc in your code, leading to an array of issues like system crashes or compromised security. To prevent such mishaps, JavaScript offers ways for handling errors appropriately which we will discuss in the upcoming sections. Stay tuned!


function sum(a, b) {
    return a * b;

console.log("sum : " + sum(10, 5));


sum : 50

An error in the­ function! Instead of summing two numbers, it’s multiplying them. But wait, the­ code still runs without any warning or interruption. This is where­ testing and debugging come into play – e­ssential practices to preve­nt such misfortunes from occurring in your code. Be sure­ to explore eve­ry possible corner case and use­ tools that can help you identify errors and fix the­m before they cre­ate any serious problems.

2. try/catch Statements in JavaScript

In JavaScript, you can avoid errors from interrupting your program by using try/catch statements. These statements test a block of code for errors and handle them with grace, without stopping the entire program’s execution.

The try block is like a brave soldier that writes the code fearlessly but might stumble upon an error. So, when it stumbles, the catch block comes in as a hero to take its place and handle the situation by providing solutions such as logging the error or offering another alternative.


try {
     // code that might produce an error
     const result = divide(10, 0);
} catch (error) {
     // handle the error

In the example, we try to divide 10 by 0 resulting in a runtime error. However, the catch block comes to play and conveniently records this occurrence in the console.

When coding, things don’t always go as planned. Sometimes errors occur and can halt the program’s execution altogether. Fortunately, a try/catch statement comes to the rescue! By using this technique, you can gracefully handle errors within your program without it crashing entirely.

In JavaScript programming, try/catch statements are a game-changing tool for handling errors. They pave the way for elegant error handling and prevent potential glitches that may cause headaches while coding.

3. Error Objects & Custom Errors in JavaScript

When coding in JavaScript, mistakes can happen. But fear not! These pesky blunders are captured and neatly packaged as objects for your convenience. You’ll get all the info you need to handle and debug errors, including details on what went wrong, where it happened (file name and line number) and more.

There are several types of error objects in JavaScript, including:

  • Error: the base error object from which other error objects inherit.
  • SyntaxError: occurs when there is a syntax error in the code.
  • ReferenceError: occurs when an attempt is made to reference an undefined variable.
  • TypeError: occurs when a value is not of the expected type.

An example of how to create and throw a custom error object in JavaScript:

class CustomError extends Error {
     constructor(message) {
 = 'CustomError';

function divideNumbers(num1, num2) {
     if (num2 === 0) {
          throw new CustomError('Cannot divide by zero');
     return num1 / num2;

try {
     var result = divideNumbers(10, 0);
} catch (error) {
     if (error instanceof CustomError) {
           console.log( + ': ' + error.message);
     } else {


CustomError: Cannot divide by zero

Let’s simplify this code example!, we define a custom error class called CustomError that extends the built-in Error class. Define a constructor that accepts a message­ as its parameter and calls the super() method to pass the message to the Error constructor. We also set the name property to ‘CustomError’.

Created a function to divide two numbers called divideNumbers, it takes 2 parameters. If the second parameter is not === zero then throw a CustomError and pass ‘Cannot divide by zero’ message. Otherwise, divide the first parameter by the second parameter and return the result.

Use try/catch statement to call the divideNumbers function with the values 10 and 0. Since the second number is zero, a CustomError is thrown. We catch the error and check if it is an instance of CustomError. If it is, we log the name and message properties of the error. If it is not, we log the error object itself.

If you want to create your error types, using error objects can come in handy. They allow you to add extra context about the issue, such as pinpointing where it occurred or storing pertinent debugging details for later reference.

When it comes to working with JavaScript, error handling is a key aspect of the coding process. This is where error objects come in handy – they act as your trusty sidekick, providing valuable information to help you troubleshoot and debug errors more effectively.

4. Debugging

JavaScript error handling is like a detective job — spotting and solving bugs are key skills of any developer. Debugging your code doesn’t only reduce frustration, but it saves you hours of hair-pulling mistakes while increasing reliability.

Here are some techniques for effective debugging in JavaScript:

  1. Console.log: When things go awry in your JavaScript code, console.log is the knight in shining armor that swoops in to save the day. With this handy tool, you can easily print out messages and values to the console, making it easier than ever to pinpoint pesky errors and restore order
  2. Debugger: The debugger is a handy tool that comes embedded in most web browsers and integrated development environments (IDEs). It enables you to halt the running of your code at specific points while checking out variable values.
  3. Step through your code: Walking step by step helps you catch pesky mistakes hiding in your work. Use the debugger or good old console.log statements to amble along and get insight into how your code operates.
  4. Check your assumptions: If you stumble upon an error, it’s crucial to pause and reassess your thinking about the code. Be absolutely certain about how it was meant to function, and make sure those thoughts genuinely align with reality before proceeding further.
  5. Break the problem down: When an error seems impossible to trace, split the problem into smaller bits. That way, you can find the root of the issue and breeze through fixing it.

Debugging in JavaScript is crucial for error-handling and code efficiency. Employing tools such as console.log and the debugger while carefully testing your assumptions can help identify issues swiftly. Ensure effective debugging for a smooth coding experience!

5. Best Practices for Error Handling in JavaScript

Effective error handling in JavaScript is crucial to prevent disastrous consequences. Don’t let mistakes in your code go unnoticed or cause unexpected errors. Follow these tips for mastering error handling like a pro:

  1. Handle errors gracefully: Errors happen, it’s inevitable. What matters is how you tackle them. You can’t afford your program to collapse or stumble out of nowhere when a user encounters an error. Coming up with informative error messages that describe the issue will save you from much trouble. And please ensure those are practical enough to help users troubleshoot on their own.
  2. Use try/catch statements: To ensure seamless program execution and expedited error resolution, incorporate try/catch statements in your code. This nifty trick can catch errors before they sabotage your code and minimize the time you spend troubleshooting potential snags.
  3. Use meaningful error messages: Error handling is essential in coding. When errors occur, ensure that you use clear and concise language in your error messages to relay necessary information about the issue. This approach speeds up troubleshooting efforts for you and other developers.
  4. Test your code:  Want to ensure smooth production? Test those lines! Thoroughly checking for errors is a must before deploying your code. It’s best practice to use both automated and manual testing tools for optimal results.
  5. Log errors: When your code goes rogue, logging errors can come to the rescue! By using tools like the console or a logging library, you can easily record any issues and track down their origin. This helps in identifying problems more effectively and saves time in debugging.

After learning and implementing best practices for handling errors in JavaScript, you’ll avoid the daunting task of combing through lines upon lines of code to fix any bugs. By incorporating try/catch statements, producing readable error messages, rigorous testing, and logging errors, debugging becomes smooth and swift.

6. Conclusion

Writing reliable and effective JavaScript code without error handling is like driving a car without brakes – you wouldn’t feel safe, would you? But with the help of try/catch statements, error objects, debugging techniques, and best practices, identifying and resolving errors becomes as easy as pressing the brake pedal.

Dealing with errors is crucial! So, don’t forget to address them gracefully. Make it easy for your users by providing informative error messages describing what went wrong and suggesting ways of fixing it. Moreover, testing your code thoroughly and logging potential issues can save you endless hours of frustration down the road by identifying bugs before they turn into a nightmare user experience. Remember: happy programming means satisfied users!

JavaScript error handling can be a tricky task, but fear not! By following these best practices, you’ll be able to write code that’s rock-solid reliable and highly effective. Better yet? Your users will love the seamless experience. No more mind-numbing bug diagnostics or aimless troubleshooting.


What is the difference between an error object and a throw statement?

A throw statement and an error object both handle errors, but they function differently. Error objects store details about the error, while throw statements send out a distress signal in the form of an exception object.

What is the purpose of error handling in JavaScript?

JavaScript error handling serves to identify and address coding errors that may arise. With effective error handling, the dependability and user-friendliness of the code can be improved substantially, giving you peace while debugging or resolving potential issues.

What are some common types of errors in JavaScript?

JavaScript has some errors that keep cropping up, such as the syntax errors, runtime errors, and logical ones. Syntax errors are simple mistakes in the code’s writing while runtime one occurs during instructions execution. The logical missteps come when there is a flaw in its reasoning structure.

What is a try/catch statement in JavaScript?

When coding, a try/catch statement is a handy block of code that can save you from potential errors. The try block contains the code that could cause an error, while the catch block houses the solution to these issues if they appear. So get your hands on those try/catch statements and avoid any programming mishaps!

What is an error object in JavaScript?

JavaScript has a handy feature called Error objects. These are objects that hold valuable information about errors that pop up while running your code. To create an error object, you can use the Error constructor function, which allows you to dive deeper into the details of the error for troubleshooting purposes.

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