Exception handling

The try-catch statement allows handling user-defined exceptions.

• No finally block: Cleanup operations must be handled manually.
• Only user-defined exceptions can be caught: Internal exceptions (such as syntax errors or out-of-memory errors) cannot be intercepted.

  ⚠️ The standard library may throw exceptions which can be caught, so always read the documentation first!

• The catch block requires a parameter: Omitting the parameter results in a syntax error.

Syntax

try {
    // Code that might throw an exception
} catch (error) {
    // Handle the exception
}

throw Keyword

The throw keyword is used to manually raise exceptions in the program. When an exception is thrown, execution stops immediately, and control is passed to the nearest try-catch block that can handle the thrown exception. Only user-defined exceptions can be caught (or those thrown by libraries), and internal exceptions cannot be intercepted.

Syntax

throw expression;

Example: Division by zero

fn divide(a, b) {
    if (b == 0) {
        throw "Division by zero is not allowed";
    }
    return a / b;
}

try {
    const result = divide(10, 0);
    console.log("Result: ", result);
} catch (err) {
    console.log("Error: ", err);  // "Error: Division by zero is not allowed"
}

Example: Throwing and Catching an Object

fn validateInput(input) {
    if (input.length === 0) {
        throw { message: "Input cannot be empty", code: 400 };
    }
    return "Valid input";
}

try {
    console.log(validateInput(""));
} catch (err) {
    console.log("Error: ", err.message, ", Code: ", err.code);
}

Notes

• throw must be followed by an expression, which can be a string, object, or any other value.
• When an exception is thrown, the program will stop executing the current function and look for a catch block to handle it.
• If no catch block is found, the program will terminate.
• The thrown object can contain additional details, such as error codes or messages, for more advanced error handling.