How to use neverthrow with async/await?

Use ResultAsync which is thenable, so you can await it, but handle errors with methods like match or unwrapOr. For example, const value = await resultAsync.unwrapOr(default) safely extracts the value or fallback.

Neverthrow vs try/catch: which is better for error handling?

Neverthrow is superior for type safety and explicit error flows in TypeScript, forcing handling at compile-time, while try/catch is simpler for quick scripts but prone to uncaught exceptions. Neverthrow's ESLint plugin enforces error consumption.

Can I use neverthrow in JavaScript without TypeScript?

Yes, it works in plain JavaScript, but you lose TypeScript benefits like type checks. The API remains functional, but errors might be harder to track without static typing.

How to wrap a function that throws exceptions with neverthrow?

Use the fromThrowable utility. For instance, const safeJsonParse = Result.fromThrowable(JSON.parse, errorMapper) converts JSON.parse to return a Result, catching any thrown errors.

What are the performance costs of neverthrow?

There's overhead from object wrappers and method calls, but it's generally negligible for most apps. Profile if performance is critical, as the library adds layers compared to raw promises.

How to ensure all errors are handled in neverthrow?

Install the optional eslint-plugin-neverthrow, which forces error consumption via match, unwrapOr, or _unsafeUnwrap, reducing bugs from unhandled Results.

NeverThrow — Type-Safe Error Handling Library

What is NeverThrow?

Neverthrow is a library for JavaScript and TypeScript that provides a `Result` type for type-safe error handling. It allows developers to represent operations that can succeed or fail as explicit `Ok` or `Err` values, eliminating the need for thrown exceptions. This makes error handling predictable, composable, and fully type-checked.

Target Audience

TypeScript and JavaScript developers building applications where robust, explicit error handling is critical, such as backend services, data processing pipelines, or any system requiring high reliability.

Value Proposition

Developers choose Neverthrow because it brings Rust-like error handling to JavaScript/TypeScript, offering compile-time safety, fluent APIs for chaining operations, and utilities to seamlessly integrate with existing promise-based or exception-throwing code.

Type-Safe Errors for JS & TypeScript

Use Cases

Best For

Building TypeScript applications with compile-time error safety
Replacing try/catch blocks with explicit, chainable error handling
Wrapping third-party libraries that throw exceptions into safe Result types
Chaining multiple fallible operations without nested conditionals
Handling asynchronous errors in a synchronous-style API
Ensuring all errors are explicitly handled via linting rules

Not Ideal For

Projects where rapid prototyping and minimal code overhead are prioritized over type safety
Teams deeply entrenched in standard promise-based error handling with async/await and try/catch
Applications with globally managed errors where explicit per-operation checking feels unnecessarily verbose
Environments with extreme performance constraints where object wrapper overhead is unacceptable

Pros & Cons

Pros

Type-Safe Error Encoding

Encapsulates success and failure in TypeScript types, eliminating uncaught exceptions and enabling compile-time checks, as shown in the Result<T, E> generic signatures throughout the API.

Fluent Composition API

Provides combinators like map, andThen, and orElse for chainable operations, allowing complex error flows without nested conditionals, similar to promises but with error awareness.

Seamless Async Integration

ResultAsync wraps Promise<Result> and is thenable, enabling synchronous-style error handling for asynchronous code without manual await chaining, detailed in the asyncAndThen and asyncMap methods.

Third-Party Exception Safety

Utilities like fromThrowable and fromAsyncThrowable convert exception-throwing functions into Result-returning ones, making it safe to integrate with libraries that use throw, as demonstrated in the wrapping examples.

Cons

Functional Programming Mindset Required

Demands familiarity with concepts like monads and combinators, which can be a steep learning curve for developers used to imperative JavaScript, evident in methods like andThen and safeTry using generators.

Boilerplate in Simple Cases

For straightforward error handling, using Results can be more verbose than try/catch, as seen in the safeTry example which requires a generator function for implicit error returns.

Dependency and Performance Overhead

Adds a third-party library to core error handling, with potential performance costs from object wrappers and method calls, though not explicitly benchmarked in the README.

Frequently Asked Questions

What is NeverThrow?

Target Audience

Value Proposition

Use Cases

Best For

Building TypeScript applications with compile-time error safety
Replacing try/catch blocks with explicit, chainable error handling
Wrapping third-party libraries that throw exceptions into safe Result types
Chaining multiple fallible operations without nested conditionals
Handling asynchronous errors in a synchronous-style API
Ensuring all errors are explicitly handled via linting rules

Not Ideal For

Projects where rapid prototyping and minimal code overhead are prioritized over type safety
Teams deeply entrenched in standard promise-based error handling with async/await and try/catch
Applications with globally managed errors where explicit per-operation checking feels unnecessarily verbose
Environments with extreme performance constraints where object wrapper overhead is unacceptable

Pros & Cons

Pros

Type-Safe Error Encoding

Encapsulates success and failure in TypeScript types, eliminating uncaught exceptions and enabling compile-time checks, as shown in the Result<T, E> generic signatures throughout the API.

Fluent Composition API

Provides combinators like map, andThen, and orElse for chainable operations, allowing complex error flows without nested conditionals, similar to promises but with error awareness.

Seamless Async Integration

ResultAsync wraps Promise<Result> and is thenable, enabling synchronous-style error handling for asynchronous code without manual await chaining, detailed in the asyncAndThen and asyncMap methods.

Third-Party Exception Safety

Cons

Functional Programming Mindset Required

Boilerplate in Simple Cases

For straightforward error handling, using Results can be more verbose than try/catch, as seen in the safeTry example which requires a generator function for implicit error returns.

Dependency and Performance Overhead

Adds a third-party library to core error handling, with potential performance costs from object wrappers and method calls, though not explicitly benchmarked in the README.

Frequently Asked Questions

NeverThrow

What is NeverThrow?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?

NeverThrow

What is NeverThrow?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?