Error Handling: try/catch/finally

Syntax

try {
} catch (error) {
} finally {
}

Examples

try {
  const data = JSON.parse("{ invalid json");
} catch (error) {
  console.log("Failed to parse:", error.message);
}

console.log("Program continues running");

function processData() {
  console.log("Starting...");
  try {
    throw new Error("Something went wrong");
  } catch (error) {
    console.log("Caught:", error.message);
  } finally {
    console.log("Cleanup runs regardless"); // always executes
  }
}

processData();

function withdraw(balance, amount) {
  if (amount > balance) {
    throw new Error("Insufficient funds");
  }
  return balance - amount;
}

try {
  withdraw(100, 150);
} catch (error) {
  console.log(error.message); // "Insufficient funds"
  console.log(error.name);    // "Error"
}

Best practices

• Only wrap code that can genuinely fail in try/catch - wrapping too much makes it harder to know what actually went wrong
• Always throw Error objects (or subclasses) rather than plain strings, so the stack trace and error.message are available
• Use finally for cleanup that must happen either way, like closing a connection or hiding a loading spinner
• Avoid using try/catch for normal control flow - reserve it for genuinely exceptional, unexpected situations

At a glance

Purpose

Application logic and interaction

File extension

.js · .mjs

Runs in

Browsers and JavaScript runtimes

Usually used with

HTML, CSS and Web APIs

Specifications & further reading

• ECMAScript specification

Related JavaScript documentation