Catcherror

Catcherror is a term used in computer programming to describe mechanisms that intercept and handle errors occurring in asynchronous data flows or computations. In practice, catcherror denotes an operation or function that captures an error from a preceding stage and produces an alternative result or sequence, rather than allowing the error to propagate unhandled.

In reactive and streaming libraries, catcherror is often realized as an operator or method named catchError or catchError. Examples include RxJS, where catchError intercepts an observable's error and returns a new observable; Dart's Stream.catchError attaches an error handler that can transform the error or provide a fallback value; Kotlin's Flow and other frameworks offer similar catch-like operators that enable downstream error handling or continuation.

Common patterns include returning a fallback value or stream when an error occurs; retrying the failed operation with backoff and a cap on attempts; mapping low-level errors to domain-specific error types; and preserving error metadata for diagnostics.

Best practices emphasize catching errors only when they can be meaningfully handled, avoiding swallowing errors without reporting, and ensuring that error handling preserves enough context for debugging. In asynchronous contexts, catcherror often interacts with scheduling and concurrency concerns, so handlers should be deterministic and side-effect-free where possible.

See also: catchError operator, error handling patterns in asynchronous programming, backoff retry.