ow
v3.1.1 MITFunction argument validation for humans
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About ow
The `ow` package addresses the common challenge of validating function arguments in JavaScript and Node.js applications. It simplifies the process of ensuring that inputs to your functions meet expected types and constraints. This is crucial for preventing runtime errors, improving code maintainability, and providing clear feedback to developers using your APIs.
Designed with developer experience in mind, `ow` focuses on providing human-readable error messages and an intuitive API. Its primary audience includes backend Node.js developers, front-end developers working with complex data structures, and teams aiming to enforce API contracts rigorously. The package promotes a proactive approach to error handling by catching invalid arguments at the function's entry point.
The core of `ow`'s API revolves around its `ow(value, label)` function, which throws an error if `value` does not meet the specified criteria defined by `label`. Labels can be simple type strings like 'string' or 'number', or more complex predicate functions and object schemas. For instance, `ow(userId, 'string')` ensures `userId` is a string, while `ow(options, { port: 'number' })` validates an object structure. The package encourages defining reusable validation rules for consistency.
`ow` integrates seamlessly into any JavaScript or Node.js project, including those using modern build tools like Webpack or Rollup. It's particularly useful in scenarios where public APIs need strict input validation, such as in library development or when building microservices. The package's small, gzipped bundle size of 11.0 kB makes it suitable even for performance-sensitive front-end applications where bundle size is a concern.
With a bundle size of just 11.0 kB (gzipped), `ow` is an efficient choice for projects mindful of their footprint. It offers a mature and stable validation solution, evidenced by its zero open issues and a history of reliable performance. The MIT license further enhances its broad applicability across commercial and open-source projects, ensuring freedom of use.
While `ow` excels at argument validation, it is not intended as a replacement for comprehensive form validation libraries in client-side applications, which often require more intricate UI feedback mechanisms. For extremely simple, trivial checks that don't warrant an external dependency, inline `typeof` checks might suffice, though they lack the expressive power and consistent error reporting of `ow`.
When to use
- When you need to enforce type checking and constraints on function arguments at runtime in Node.js or browser environments.
- When developing libraries or APIs where clear contract enforcement and informative error messages for incorrect usage are paramount.
- When validating complex object structures or array contents using `ow`'s predicate functions and schema definitions.
- When integrating with frameworks that require strict argument validation for public-facing functions or internal services.
- When aiming for robust error handling by catching invalid inputs early in the execution flow.
- When you want to maintain a concise bundle size, as `ow` is only 11.0 kB gzipped.
When NOT to use
- If you only need to perform basic type checks like `typeof x === 'string'` and do not require descriptive error messages.
- If your project is a client-side application with complex form interactions requiring dedicated UI validation libraries that handle user feedback.
- When the overhead of adding any external dependency, however small, is not justifiable for the validation needs.
- If you are already using a comprehensive validation library that covers all your project's requirements.
- For validating data structures that are extremely simple and inherently safe, where explicit checks would be redundant.