JavaScript Error Handling: try...catch

JavaScript Error Handling: try...catch

Error handling in JavaScript helps prevent scripts from crashing when unexpected issues arise. The try...catch statement allows you to handle errors gracefully.

🔹 Basic try...catch Syntax

try {
    // Code that might throw an error
} catch (error) {
    // Code to handle the error
}

✔️ The try block runs the code and checks for errors.
✔️ The catch block runs if an error occurs.

🔹 Example: Handling Errors Gracefully

try {
    let result = 10 / 0;
    console.log("Result:", result); // ✅ Works, since division by zero returns Infinity
} catch (error) {
    console.log("An error occurred:", error.message);
}

✔️ No error occurs, so the catch block is skipped.

Handling an Actual Error

try {
    let num = undefinedVariable * 2; // ❌ This will throw an error
} catch (error) {
    console.log("An error occurred:", error.message);
}

✅ Output:

An error occurred: undefinedVariable is not defined

✔️ The script doesn’t crash, and we get an error message instead.

🔹 Using finally for Cleanup

The finally block always runs, whether an error occurs or not.

try {
    console.log("Trying...");
    let num = 10 / 0;
} catch (error) {
    console.log("Error:", error.message);
} finally {
    console.log("Cleanup done.");
}

✅ Output:

Trying...
Cleanup done.

✔️ Use finally to release resources (e.g., close files, stop a loader).

🔹 Throwing Custom Errors

You can manually throw errors using throw.

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

try {
    console.log(divide(10, 0)); // ❌ Error thrown here
} catch (error) {
    console.log("Caught Error:", error.message);
}

✅ Output:

Caught Error: Cannot divide by zero

✔️ throw let's you define custom error messages.

🔹 Handling Specific Errors with instanceof

Different errors can be handled individually.

try {
    JSON.parse("{ invalid json }"); // ❌ SyntaxError
} catch (error) {
    if (error instanceof SyntaxError) {
        console.log("Invalid JSON:", error.message);
    } else {
        console.log("Unknown error:", error.message);
    }
}

✅ Output:

Invalid JSON: Unexpected token i in JSON at position 2

✔️ This is useful when handling different error types.

🔹 Summary

✅ try → Runs the code that might fail
✅ catch → Handles errors if they occur
✅ finally → Runs cleanup code, no matter what
✅ throw → Manually generate errors
✅ instanceof → Handle specific error types

🚀 Need more examples? Let me know! 😊