Defer.js

A very ligthweigth twisted.web type implementation for node.js for full async progamming

install: (not packaged yet. Coming very soon !)

npm defer

sample usage:

The difference between chained defers and defered lists is that chain defer wil take the output value of the last callback to the next and defered_lists will take args as argument and will input those args on the callback or errback

add callbacks and errback

var defer = require('./index.js')
// var defer = require('defer')
function _cb(value){
var ret = value *2;
console.log("ret1: "+ ret);
return ret;
}
function _eb(err, value){
console.log("err : "+ err);
return err;
}
function _main(a){	
var d = defer.Deferred();
var b =2;
var ret = a+b;
d.addCallback(_cb);
d.addCallback(_cb);
d.addErrback(_eb);
d.returnValue(ret);
}
_main(1);
>> Will output 6 and 12

add promises and use fallback on rejection

//Promises will compare the output value of a callback returning a boolean. If the condition is true the promise will fire next callback if not it will fire the fallback.
//Syntax: addPromise([<operator>, <value>],[<operator>, <value>] )
//Note that multiple argument array will pass each condition in turn and will fire callback only if all returned true. 
//Let's use callbacks and fallbacks and errbacks in the same logic
function _main3(a){
function _cb(value){
var ret = value *2;
console.log("ret1: "+ ret);
return ret;
}
function _eb(err, value){
console.log("err : "+ err);
return err;
}
function _fb(value){
var ret = value +1;
console.log("ret fb: "+ ret);
return ret;
}
console.log("Starting main3 example function");		
var d = defer.Deferred();
var b =2;
var ret = a+b;
d.addCallback(_cb);
d.addFallback(_fb);
d.addPromise(["<","6"]);
d.addErrback(_eb);
d.returnValue(ret);
}
_main3(1);
>> output promise has succeded value (1+2) was lower than 6 and then it fired_fb that added 1 = output 4

add defered_list callbacks and errbacks

var defer = require("./index.js");
// var defer =  require('defer');

function _cb(value){
    var ret = value *2;
    console.log("ret1: "+ ret);
    return ret;
}
function _fb(value){
var ret = value +1;
console.log("ret fb: "+ ret);
return ret;
}
function _cb222(value, value2){
    var ret = value *2+value2;
    console.log("ret222: "+ ret);
    return ret;
}
function _cb2(value){
    var ret = value *2;
    console.log("ret2: "+ ret);
    return ret;
}
function _cb3(value){
    var ret = value *2;
    console.log("ret3: "+ ret);
    return ret;
}
function _cb4(value){
    var ret = value *2;
    console.log("ret4: "+ ret);
    return ret;
}
function _eb(err, value){
    console.log("err : "+ err);
    return err;
}
function _eb2(err, value){
    console.log("err : "+ err);
    return err;
}
//Let's chain our callbacks that must pass its return value to the next one
// <defered object>.defered_list_addCallback(callback)
// <defered object>.defered_list_addErrback(errback)
// will fire in case of a undefined or null value or not function cb or err
function _main(a){
	var d = defer.Deferred();
	var b =2;
	var ret = a+b;
	d.addCallback(_cb);
	d.addCallback(_cb2);
	d.addCallback(_cb3);
	d.addCallback(_cb4);
	d.addErrback(_eb);
	d.addErrback(_eb2);
	d.returnValue(ret);
}
_main(1);// output 6 12 24 48

//Let's pile our callbacks that must be resolved independently ans will take their own arguments
// <defered object>.defered_list_addCallback(callback, [args])
// <defered object>.defered_list_addErrback(errback, [args])
// will fire in case of a undefined or null value or not function cb or err
function _main2(a){
	var dl = defer.defered_list();
	var b =2;
	var ret = a+b;
	dl.defered_list_addCallback(_cb222, [1,2]);
	dl.defered_list_addCallback(_cb2 , [1]);
	dl.defered_list_addCallback(_cb3, [1]);
	dl.defered_list_addCallback(_cb4, [1]);
	dl.defered_list_addErrback(_eb, [1]);
	dl.defered_list_addErrback(_eb2, [1]);
	dl.defered_list_returnValue(ret);
}
_main2(1);// output 4 2 2 2
//Let's use callbacks and fallbacks and errbacks in the same logic
function _main3(a){
console.log("Starting main3 example function");		
var d = defer.Deferred();
var b =2;
var ret = a+b;
d.addCallback(_cb);
d.addFallback(_fb);
d.addPromise(["<","6"]);
d.addErrback(_eb);
d.returnValue(ret);
}
_main3(1);// output promise has succeded value (1+2) was lower than 6 and then it fired_fb that added 1 = output 4

Tests:

Install mocha globally to use it from terminal

npm install mocha -g

then do the following command in the node-modules root

mocha