mimic-fn

What is mimic-fn?

The mimic-fn package is a utility that allows you to copy the properties of a function onto another function. This includes the function's name, length (the number of arguments it expects), and custom properties. It is useful when you want to wrap a function without losing its original properties, which can be important for debugging, introspection, and certain function-based APIs that rely on these properties.

What are mimic-fn's main functionalities?

Copying function properties

This feature allows you to copy all properties from the original function to the wrapper function, including the function name and custom properties.

const mimicFn = require('mimic-fn');

function original() {}
original.customProp = 'hello';

function wrapper() {
  return original();
}

console.log(wrapper.name); // 'wrapper'
console.log(wrapper.customProp); // undefined

mimicFn(wrapper, original);

console.log(wrapper.name); // 'original'
console.log(wrapper.customProp); // 'hello'

Other packages similar to mimic-fn

rename-function

The rename-function package allows you to change the name of a function, which is one aspect of what mimic-fn does. However, it does not handle copying other properties or the function's length.

README

Make a function mimic another one

Useful when you wrap a function in another function and like to preserve the original name and other properties.

Install

$ npm install mimic-fn

Usage

const mimicFn = require('mimic-fn');

function foo() {}
foo.unicorn = '🦄';

function wrapper() {
	return foo();
}

console.log(wrapper.name);
//=> 'wrapper'

mimicFn(wrapper, foo);

console.log(wrapper.name);
//=> 'foo'

console.log(wrapper.unicorn);
//=> '🦄'

console.log(String(wrapper));
//=> '/* Wrapped with wrapper() */\nfunction foo() {}'

API

mimicFn(to, from, options?)

Modifies the to function to mimic the from function. Returns the to function.

name, displayName, and any other properties of from are copied. The length property is not copied. Prototype, class, and inherited properties are copied.

to.toString() will return the same as from.toString() but prepended with a Wrapped with to() comment.

to

Type: Function

Mimicking function.

from

Type: Function

Function to mimic.

options

Type: object

ignoreNonConfigurable

Type: boolean
Default: false

Skip modifying non-configurable properties instead of throwing an error.

Related

• rename-fn - Rename a function
• keep-func-props - Wrap a function without changing its name and other properties

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