Defining Custom Error Types
When handling errors in JavaScript, you will often encounter situations where the built-in error types like Error, TypeError, or ReferenceError do not provide enough detail about what went wrong in your application. Using custom error types allows you to describe specific problems in your code more clearly. You should use custom error types when you need to distinguish between different error conditions in your application, provide more helpful messages, or attach additional information to errors for debugging and logging. Custom error types make your code easier to read, maintain, and debug, especially in larger or more complex projects.
123456789101112131415161718192021222324class ValidationError extends Error { constructor(message) { super(message); this.name = "ValidationError"; } } // Usage example function processUserInput(input) { if (typeof input !== "string") { throw new ValidationError("Input must be a string."); } return input.trim(); } try { processUserInput(42); } catch (err) { if (err instanceof ValidationError) { console.error("Validation failed:", err.message); } else { console.error("Unknown error:", err); } }
In this example, you define a ValidationError class that extends the built-in Error class. By setting the name property, you make it clear what kind of error occurred. When processUserInput receives an invalid input, it throws a ValidationError with a descriptive message. In the try...catch block, you can check the error type using instanceof to handle validation errors differently from other errors. This approach leads to more descriptive error messages, easier debugging, and better separation of concerns in your code. Custom error types are powerful tools for building robust and maintainable JavaScript applications.
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When handling errors in JavaScript, you will often encounter situations where the built-in error types like Error, TypeError, or ReferenceError do not provide enough detail about what went wrong in your application. Using custom error types allows you to describe specific problems in your code more clearly. You should use custom error types when you need to distinguish between different error conditions in your application, provide more helpful messages, or attach additional information to errors for debugging and logging. Custom error types make your code easier to read, maintain, and debug, especially in larger or more complex projects.
123456789101112131415161718192021222324class ValidationError extends Error { constructor(message) { super(message); this.name = "ValidationError"; } } // Usage example function processUserInput(input) { if (typeof input !== "string") { throw new ValidationError("Input must be a string."); } return input.trim(); } try { processUserInput(42); } catch (err) { if (err instanceof ValidationError) { console.error("Validation failed:", err.message); } else { console.error("Unknown error:", err); } }
In this example, you define a ValidationError class that extends the built-in Error class. By setting the name property, you make it clear what kind of error occurred. When processUserInput receives an invalid input, it throws a ValidationError with a descriptive message. In the try...catch block, you can check the error type using instanceof to handle validation errors differently from other errors. This approach leads to more descriptive error messages, easier debugging, and better separation of concerns in your code. Custom error types are powerful tools for building robust and maintainable JavaScript applications.
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