# universalify [](https://travis-ci.org/RyanZim/universalify)    Make a callback- or promise-based function support both promises and callbacks. Uses the native promise implementation. ## Installation ```bash npm install universalify ``` ## API ### `universalify.fromCallback(fn)` Takes a callback-based function to universalify, and returns the universalified function. Function must take a callback as the last parameter that will be called with the signature `(error, result)`. `universalify` does not support calling the callback with more than three arguments, and does not ensure that the callback is only called once. ```js function callbackFn (n, cb) { setTimeout(() => cb(null, n), 15) } const fn = universalify.fromCallback(callbackFn) // Works with Promises: fn('Hello World!') .then(result => console.log(result)) // -> Hello World! .catch(error => console.error(error)) // Works with Callbacks: fn('Hi!', (error, result) => { if (error) return console.error(error) console.log(result) // -> Hi! }) ``` ### `universalify.fromPromise(fn)` Takes a promise-based function to universalify, and returns the universalified function. Function must return a valid JS promise. `universalify` does not ensure that a valid promise is returned. ```js function promiseFn (n) { return new Promise(resolve => { setTimeout(() => resolve(n), 15) }) } const fn = universalify.fromPromise(promiseFn) // Works with Promises: fn('Hello World!') .then(result => console.log(result)) // -> Hello World! .catch(error => console.error(error)) // Works with Callbacks: fn('Hi!', (error, result) => { if (error) return console.error(error) console.log(result) // -> Hi! }) ``` ## License MIT