I am currently attempting to learn the AngularJS framework and I keep hearing about something called "promise". I have researched a little about it, although I cannot seem to find a thorough explanation to how and when to use "promises".
Can anyone please explain and provide a solution between using a promise, and not using a promise. What is the advantage of using a promise over not using one?
All answer are appreciated.
Thanks.
promises implementation basically provides an interface which define at least one method 'when' that return therefore, a "Promise", thus a result from an async operation.
Advantages are better code readability (and production as well), better reuse of the results without incurring on the scaring "callbacks hell", chainabilty, etc...
A simple scenario with jQuery:
without promises
$.ajax({
url: someurl,
success: function(data)
{
//do something with data
}
});
with promises
var p = $.ajax({ url: someurl });
$.when(p).then(function(data)
{
//do something with data
});
However, a better explanation: http://wiki.commonjs.org/wiki/Promises/A
The official documentation says that
The promise api allows for composition that is very hard to do with the traditional callback (CPS ) approach. For more on this please see the Q documentation especially the section on serial or parallel joining of promises.
http://docs.angularjs.org/api/ng/service/$q
I think the easiest explanation could be that it's a much better and cleaner way to do a serial or very complex callbacks than the traditional way.
This is the link you can read more about the benefit of using promise:
