Wrapper Function (wfn)

Ensures that a wrapper function has the same properties as the underlying function, such as name and length. When toString() is called on the wrapper function, the code of the original function is shown, together with a comment identifying the wrapper(s).

Installation

Requires Node.js 6.0.0 or above.

npm i wfn

API

The module exports a single function.

Parameters

1. fn (Function): The underlying function
2. wrapper (Function): The wrapper function that calls fn

Return Value

The modified wrapper function

Usage

const wfn = require('wfn')

function func (a, b, c) { return 'result' }
function wrapper () { return func() }

wrapper() // 'result'

// Before
wrapper.name // 'wrapper'
wrapper.length // 0
wrapper.toString() // 'function wrapper () { return func() }'

// Apply the module
wfn(func, wrapper)

// After
wrapper.name // 'func'
wrapper.length // 3
wrapper.toString() // 'function func (a, b, c) { return 'result' } /* [wfn] Wrapped with wrapper() */'

Wrapper Function Stringification

In the above example, note that the wrapper’s toString() method produces the code of the underlying function — not of the wrapper — but with a comment notation that the function has been wrapped.

If you wrap a function more than once, wfn will recognize this and will generate a comment notation that mentions all the wrappers. Consider the following example:

function original () {
  return 'value'
}

const wrapper1 = wfn(original, function wrapper1 () { return original() })
const wrapper2 = wfn(wrapper1, () => wrapper1())
const wrapper3 = wfn(wrapper2, function wrapper3 () { return wrapper2() })

If you call wrapper3.toString(), you will get the following:

function original () {
  /* [wfn] Wrapped with wrapper1(), wrapper3(), and 1 other unnamed function */
  return 'value'
}

If this is something you absolutely don’t care about, and you only want properties like name and length copied, consider swapping out this module for copy-own so you have less overhead.

Related

For more projects like this, check out @lamansky/fn.