promise-toolbox/promisify.js

Essential utils for promises

"use strict";

const setFunctionNameAndLength = require("./_setFunctionNameAndLength");

const promisify = (fn, context) => setFunctionNameAndLength(function () {
  const length = arguments.length;
  const args = new Array(length + 1);

  for (let i = 0; i < length; ++i) {
    args[i] = arguments[i];
  }

  return new Promise((resolve, reject) => {
    args[length] = (error, result) => error != null && error !== false ? reject(error) : resolve(result);

    fn.apply(context === undefined ? this : context, args);
  });
}, fn.name, fn.length - 1);

module.exports = promisify;