Currying Use Cases and Best Practices
When to use currying and best practices in modern JavaScript.
Currying Use Cases and Best Practices
When to Use Currying
- Partial application: preset configuration.
const get = curry((url, params) => fetch(url, params)); const getApi = get('/api'); - Function composition: chain with compose/pipe.
pipe(filter(isEven), map(double), reduce(sum)) - Event handlers: preset context.
const handleClick = curry((action, event) => ...); const deleteClick = handleClick('delete'); - Logging: preset level.
const log = curry((level, msg) => ...); const error = log('ERROR');
Best Practices
- Use the generic curry function instead of manual nesting.
- Do not over-curry simple functions. Currying adds complexity.
- Use with compose/pipe for functional pipelines.
- Order arguments from most to least specific (config first, data last).
- Consider libraries like lodash (
_.curry) for production code.
When NOT to Use Currying
- Simple functions with 2-3 arguments.
- When readability suffers.
- In performance-critical code (closures have a small overhead).
- When the team is not familiar with functional programming.
The Takeaway
Use currying for: partial application (preset config), composition (functional pipelines), event handlers (preset action), and logging (preset level). Best practices: use generic curry, do not over-curry, order args (config first, data last). Do not use for simple functions or when readability suffers.
For partial application (preset configuration), function composition (pipe with filter/map/reduce), event handlers (preset action), and logging (preset level). Use when you need reusable, configurable functions.
For simple functions with 2-3 arguments (currying adds unnecessary complexity), when readability suffers, in performance-critical code (closures have overhead), and when the team is not familiar with functional programming.
Most specific first, least specific last. Configuration first, data last. For example: curry((baseUrl, endpoint, params) => ...) so you can preset baseUrl and endpoint, then pass params at call time.
Use the generic curry function. It is reusable and handles any number of arguments. Manual currying (nested functions) is verbose and error-prone for functions with many arguments.
Yes, a small one. Each curried call creates a new closure. In hot code paths, this can add up. For most applications, the overhead is negligible. Avoid currying in performance-critical inner loops.
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