try...catch & Error Handling

try...catch is used to safely handle errors in synchronous and asynchronous code, preventing crashes and allowing custom responses.

1. Basic Syntax

try {
  // Code that might throw an error
} catch (err) {
  // Runs if error occurs
}

Example:

try {
  let x = y + 1; // y is not defined → error
} catch (err) {
  console.log("Error caught:", err.message);
}

2. finally Block

Always runs, whether error occurs or not.

try {
  // risky code
} catch (err) {
  console.log("Handled error");
} finally {
  console.log("This always runs");
}

3. Error Object

In catch(err), the err object contains:

• name: error type (e.g. ReferenceError)
• message: description
• stack: call trace (for debugging)

try {
  throw new Error("Something went wrong");
} catch (e) {
  console.log(e.name);    // Error
  console.log(e.message); // Something went wrong
}

4. Handling Errors in Functions

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

try {
  console.log(divide(10, 0));
} catch (err) {
  console.log("Math error:", err.message);
}

5. Async + try/catch

Always wrap await calls in try/catch.

async function fetchData() {
  try {
    let res = await fetch("invalid-url");
    let data = await res.json();
  } catch (err) {
    console.log("Fetch failed:", err.message);
  }
}

6. Best Practices

• Use try/catch around isolated risky logic
• Don’t overuse — handle only expected errors
• Use finally for cleanup tasks (e.g. closing connections, hiding loaders)
• Throw custom errors to improve debugging and user messages