@keymux/promisr

Promisr

Promisr provides a collection of utilities for expanding promise functionality.

Compatibility

Node Version	Build status
v6.10.2	TBD

Install

npm install @keymux/promisr

yarn add @keymux/promisr

Features

promisify

Promisify returns a function which returns a promise to execute a callback-based function and provides the error in a rejection or the result in a resolution.

Promisify assumes the callback function definition is:

function (error, result)

Example

const fs = require("fs");
const path = require("path");

const { promisify } = require("@keymux/promisr");

const fileToRead = path.resolve("path/to/file");
const fsOptions = {};

// If you're having trouble understanding this function call,
// I recommend reading up on currying.
const readFilePromise =
  promisify(fs.readFile)(fileToRead, fsOptions)
  .then(fileContents => {
    console.log(fileContents);
  }).catch(fsError => {
    console.error(fsError);
  });

promisifyCreator

promisifyCreator creates a custom promisify for alternative callback function definitions. promisifyCreator still assumes the callback is the last argument in the list.

Example

const doStuff = (arg, cb) =>
  const error = undefined;
  const exitCode = 0;
  const result = "some result";

  cb(error, exitCode, result);
};

const doStuffPromise = promisifyCreator((resolve, reject) => (error, exitCode, result) => {
  if (error) reject(error);
  resolve(result);
});