keep-func-props

Wrap a function without changing its name and other properties.

Function wrappers return a new function which means the original function's name and other properties are usually lost. This module enhances them to keep those properties instead.

The new function will also print the original function's body when stringified.

Function wrappers are commonly used in functional programming. They take a function as input and return it wrapped. Examples include memoizing or ensuring a function is only called once.

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Example

import keepFuncProps from 'keep-func-props'
// Any function wrapper works
import memoize from 'lodash/memoize.js'

const betterMemoize = keepFuncProps(memoize)

const anyFunction = () => true

// Function `name` and other properties are kept
console.log(anyFunction) // `[Function: anyFunction]`
console.log(memoize(anyFunction)) // `[Function: memoized]`
console.log(betterMemoize(anyFunction)) // `[Function: anyFunction]`

// Function body is kept when stringified
console.log(String(anyFunction))
// () => true
console.log(String(memoize(anyFunction)))
// function() {
//   var args = arguments,
//   key = resolver ? resolver.apply(this, args) : args[0],
//   cache = memoized.cache;
//   ...
// }
console.log(String(betterMemoize(anyFunction)))
// /* Wrapped with memoized() */
// () => true

Demo

You can try this library:

• either directly in your browser.
• or by executing the examples files in a terminal.

Install

npm install keep-func-props

This package works in both Node.js >=18.18.0 and browsers.

This is an ES module. It must be loaded using an import or import() statement, not require(). If TypeScript is used, it must be configured to output ES modules, not CommonJS.

Usage

import keepFuncProps from 'keep-func-props'

// Any function wrapper works
const wrapper =
  (anyFunction) =>
  (...args) =>
    anyFunction(...args)

// `betterWrapper` is like `wrapper` but it keeps the function properties
const betterWrapper = keepFuncProps(wrapper)

keepFuncProps(wrapper)

wrapper: (anyFunction, [...args]) => newFunction
Returns: new wrapper

A function wrapper is passed as argument. A copy of it is returned.

See also

• mimic-function: same but for functions that do not wrap other functions.

Support

For any question, don't hesitate to submit an issue on GitHub.

Everyone is welcome regardless of personal background. We enforce a Code of conduct in order to promote a positive and inclusive environment.

Contributing

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If the documentation is unclear or has a typo, please click on the page's Edit button (pencil icon) and suggest a correction.

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