JavaScript Error Handling – try, catch, finally, and throw

In JavaScript, error handling is essential to ensure your code runs smoothly, even when unexpected things happen. The keywords try, catch, finally, and throw allow you to manage errors gracefully.

1. try...catch – Catch Runtime Errors

Example:

try {
  let result = 10 / 0;
  console.log("Result:", result);
} catch (error) {
  console.log("An error occurred:", error.message);
}

Output

No error here, but if something goes wrong in the try block, the catch block will handle it.

Example with Actual Error:

try {
  undefinedFunction(); // this function doesn't exist
} catch (error) {
  console.log("Error caught:", error.message);
}

Output

Use When: You want to prevent your app from crashing due to unexpected errors.

2. throw – Create Custom Errors

You can create and throw your own errors using throw.

Example:

function divide(a, b) {
  if (b === 0) {
    throw new Error("Cannot divide by zero!");
  }
  return a / b;
}

try {
  console.log(divide(10, 0));
} catch (e) {
  console.log("Caught Error:", e.message);
}

Output

Use When: You want to trigger a custom error based on a condition.

3. finally – Always Executes

The finally block runs no matter what — even if there's an error.

Example:

try {
  console.log("Trying something...");
  // some code that may throw
} catch (err) {
  console.log("Caught an error!");
} finally {
  console.log("This always runs.");
}

Output

Use When: You need cleanup actions like closing a connection, logging, or hiding a loader.

Real-World Use Case: Form Validation

function validateForm(name) {
  if (name === "") {
    throw new Error("Name field is required.");
  }
  return "Form submitted!";
}

try {
  console.log(validateForm(""));
} catch (e) {
  console.log("Validation Error:", e.message);
} finally {
  console.log("Form check complete.");
}

Output