Error Handling (try-catch)

🟨 JavaScript Lesson 14 Advanced

Errors can halt code execution unexpectedly. Managing errors using try-catch blocks keeps your applications running robustly.

1 Try-Catch-Finally flow control

Error statements handle exceptions safely:

try: Wraps code blocks that may throw exceptions.
catch: Intercepts and handles errors if they occur, preventing application crashes.
finally: Executes cleanup code after try/catch, regardless of whether an error was thrown.
throw: Manually raises custom exceptions using `throw new Error("Message")`.

2 Exception Interception Code

Let's run a program throwing exceptions, trapping them in try-catch, and printing validation warnings:

JavaScript — Exception Handling ▶ Run Code

function parseAge(age) {
    if (age < 0) {
        throw new Error("Age cannot be negative.");
    }
    return `Age verified: ${age}`;
}

try {
    console.log(parseAge(25));
    // Try passing invalid input
    console.log(parseAge(-5));
} catch (e) {
    console.log("Exception caught: " + e.message);
} finally {
    console.log("Validation checklist finished.");
}

console.log("Application continues running smoothly...");

3 Code Challenge

Challenge: Write a function that accepts a JSON string and parses it using `JSON.parse`. Wrap this parsing operation in a try-catch block to handle invalid JSON syntax strings gracefully, and print a custom error message if parsing fails.