Error Handling in js

What is Error Handling?

Error handling is the process of managing errors that occur during program execution so that the application doesn't crash unexpectedly.

JavaScript provides:

• try
• catch
• finally
• Throw

Why Error Handling?

Without error handling:

console.log("Start");
let result = 10 / x; // x is not defined
console.log("End");

Output:

Start
ReferenceError: x is not defined

The program stops when the error occurs.

1. try...catch

• The try block contains code that may cause an error.
• The catch block handles the error.

Syntax

try {
    // risky code
} catch(error) {
    // handle error
}

Example

try {
    console.log(x);
} catch(error) {
    console.log("Error occurred");
}

Output:

Error occurred

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2. Accessing Error Information:

The error object contains details about the error.

try {
    console.log(x);
} catch(error) {
    console.log(error);
}

Output:

ReferenceError: x is not defined

Useful Properties

try {
    console.log(x);
} catch(error) {
    console.log(error.name);
    console.log(error.message);
}

Output:

ReferenceError
x is not defined

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3. finally

• The finally block always executes whether an error occurs or not.

try {
    console.log("Try block");
} catch(error) {
    console.log("Catch block");
} finally {
    console.log("Finally block");
}

Output:

Try block
Finally block

Example with Error

try {
    console.log(x);
} catch(error) {
    console.log("Error handled");
} finally {
    console.log("Always executes");
}

Output:

Error handled
Always executes

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4. throw

• The throw keyword is used to create custom errors.

Example

let age = 15;

try {
    if (age < 18) {
        throw new Error("You must be 18 or older");
    }

    console.log("Eligible");
} catch(error) {
    console.log(error.message);
}

Output:

You must be 18 or older

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