promise/lib/node-extensions.js

'use strict';

// This file contains then/promise specific extensions that are only useful
// for node.js interop

var Promise = require('./core.js');
var asap = require('asap');

module.exports = Promise;

/* Static Functions */

Promise.denodeify = function (fn, argumentCount) {
  argumentCount = argumentCount || Infinity;
  return function () {
    var self = this;
    var args = Array.prototype.slice.call(arguments, 0,
        argumentCount > 0 ? argumentCount : 0);
    return new Promise(function (resolve, reject) {
      args.push(function (err, res) {
        if (err) reject(err);
        else resolve(res);
      })
      var res = fn.apply(self, args);
      if (res &&
        (
          typeof res === 'object' ||
          typeof res === 'function'
        ) &&
        typeof res.then === 'function'
      ) {
        resolve(res);
      }
    })
  }
}
Promise.nodeify = function (fn) {
  return function () {
    var args = Array.prototype.slice.call(arguments);
    var callback =
      typeof args[args.length - 1] === 'function' ? args.pop() : null;
    var ctx = this;
    try {
      return fn.apply(this, arguments).nodeify(callback, ctx);
    } catch (ex) {
      if (callback === null || typeof callback == 'undefined') {
        return new Promise(function (resolve, reject) {
          reject(ex);
        });
      } else {
        asap(function () {
          callback.call(ctx, ex);
        })
      }
    }
  }
}

Promise.prototype.nodeify = function (callback, ctx) {
  if (typeof callback != 'function') return this;

  this.then(function (value) {
    asap(function () {
      callback.call(ctx, null, value);
    });
  }, function (err) {
    asap(function () {
      callback.call(ctx, err);
    });
  });
}