Qualified Function (qfn)

Wraps a function so it only gets executed if a condition is true.

Installation

Requires Node.js 6.0.0 or above.

npm i qfn

API

The module exports a single function.

Parameters

1. Bindable: fn (function): The underlying function that may or may not get called, depending on test.
2. test (function or boolean): A boolean indicating whether fn should be called, or a function that returns such a boolean. If test is a function, it will be given all the arguments passed to the returned function.

Return Value

A function which, when called, returns the return value of fn, if test is true. If test is false, the function returns the first argument passed to it.

Example

const qfn = require('qfn')

function add1 (x) {
  return x + 1
}

qfn(add1, true)(3) // 4
qfn(add1, false)(3) // 3

const add1IfEven = qfn(add1, x => x % 2 === 0)
add1IfEven(3) // 3
add1IfEven(4) // 5

Related

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