Promise.js

This library provides a Promises/A+ compatible Promise object, as well as providing a method for wrapping your object's methods with promise-like API.

The library is both CommonJS and AMD compatible.

Installation

npm install arieh-promise

Basic Usage

A Promise's constructor can either relieve a function or another promise as its parameters. In case a function was provided, that function would receive 2 parameters - a fulfill function and a reject function:

var promise = new Promise(function(fulfill, reject){
    var value = someOperation();

    if (value){
        fulfill(value);
    }else{
        reject('no value');
    }
});

If a promise was provided, the new Promise would fulfill/reject according to provided promise. If no parameter was provided, you can still fulfill/reject the promise via it's fulfill and reject methods.

Promise.extend

In addition to providing the basic implementation of the Promise API, this library also allows you to create chainable promise APIs for you objects.

For example - let's say we have the following object:

var obj = {
    async : function(){
        return new Promise(function(f,r){
            //some async operation
        });
    },
    setA : function(a){ this.a = a;}
};

Using Promise.extend, we can make obj's async method create a costume promise object that will provide a deffered access to obj's methods:

obj.Promise = Promise.extend(obj, ['setA']);
obj.async = function(){
    return new obj.Promise(function(f,r){
        //some async operation
    });
};

obj.async().setA('a');
obj.a; //undefined
//after async was completed:
obj.a; //'a'

What's cool about these new costume Promises is that all API points return new promises, so the same error handling mechanism governs them. This way:

obj.async()
   .then(function(){
      //do somthing
   })
   .setA('a')
   .then(fuction(){
      throw "test error";
   })
   .setA('b')
   .then(function(){}, function(e){
      console.log(obj.a);//a
      console.log(e);//test error
   });