JavaScript Error Handling — Write Safer Code

What Are Errors in JavaScript?

👉 Errors are unexpected problems that occur while your code is running.

They stop your program and can break your app if not handled properly.

Example: Runtime Error

console.log(user.name);

👉 If user is not defined → ❌ Error

ReferenceError: user is not defined

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Types of Errors (Simple View)

• Syntax Error → wrong code format

• Runtime Error → happens during execution

• Logical Error → code runs but gives wrong result

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Why Error Handling Matters

Without error handling:

• App crashes 💥

• Bad user experience 😞

• Hard to debug 🔍

With error handling:

• App fails gracefully ✅

• You can show friendly messages

• Easier debugging

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Using try...catch

👉 try...catch lets you handle errors safely

✅ Example

try {
  let result = riskyFunction();
  console.log(result);
} catch (error) {
  console.log("Something went wrong:", error.message);
}

👉 Code inside try runs

👉 If error occurs → catch handles it

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The finally Block

👉 finally always runs (whether error happens or not)

✅ Example

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

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Throwing Custom Errors

👉 You can create your own errors using throw

✅ Example

function withdraw(amount) {
  if (amount > 1000) {
    throw new Error("Limit exceeded");
  }
  return "Transaction successful";
}

try {
  withdraw(2000);
} catch (err) {
  console.log(err.message);
}

👉 Helps you control error behavior

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Graceful Failure (Important Concept)

Instead of crashing:
👉 Show useful messages

try {
  let data = JSON.parse("invalid json");
} catch (err) {
  console.log("Invalid data format");
}

👉 User doesn’t see scary errors 👌

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Real-World Example

async function fetchData() {
  try {
    const res = await fetch("https://api.example.com/data");
    const data = await res.json();
    console.log(data);
  } catch (error) {
    console.log("Failed to fetch data");
  } finally {
    console.log("Request completed");
  }
}

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Benefits of Error Handling

• Prevent crashes 💥

• Improve user experience 😊

• Easier debugging 🔍

• Better code quality 📈

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Final Thoughts

👉 Errors are normal in programming
👉 Handling them properly makes you a professional developer