1️⃣4️⃣ JavaScript Error Handling

JavaScript Error Handling helps you manage runtime errors so your program doesn’t crash unexpectedly. Let’s break down each keyword clearly:

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🔹 1. try

The try block contains code that might cause an error.

👉 JavaScript will attempt to run this code.

try {
  let result = 10 / x; // x is not defined → error
}

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🔹 2. catch

The catch block runs if an error occurs in try.

👉 It receives the error object (you can name it anything, usually err).

try {
  let result = 10 / x;
} catch (err) {
  console.log("Error occurred:", err.message);
}

✔ Output:

Error occurred: x is not defined

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🔹 3. finally

The finally block always executes, whether an error happens or not.

👉 Useful for cleanup tasks (closing connections, stopping loaders, etc.)

try {
  console.log("Trying...");
} catch (err) {
  console.log("Error:", err.message);
} finally {
  console.log("This always runs");
}

✔ Output:

Trying...
This always runs

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🔹 4. throw

The throw statement is used to create your own custom error.

👉 You can throw:

• String
• Number
• Boolean
• Object (best practice: use Error)

function checkAge(age) {
  if (age < 18) {
    throw new Error("You must be 18 or older");
  }
  return "Access granted";
}try {
  console.log(checkAge(16));
} catch (err) {
  console.log(err.message);
}

✔ Output:

You must be 18 or older

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🔥 Full Example (All Together)

try {
  let age = 15;  if (age < 18) {
    throw new Error("Underage user");
  }  console.log("Access granted");} catch (err) {
  console.log("Caught error:", err.message);} finally {
  console.log("Execution finished");
}

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🧠 Key Points

• try → test code
• catch → handle errors
• finally → always runs
• throw → create custom errors

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🚀 Interview Tip

• Always use Error object in throw:

throw new Error("Something went wrong");