IT:AD:Promise
- See also:
Summary
A Promise is a deferred action.
THere's nothing inherently wrong will callbacks – just that they get a bit unwieldy when things get complex.
doSomethingThatWill = function(data,callback){
if (doWhatever){
if (successCallback){successCallback()}
}else{
if (errorCallback){errorCallback()}
}
}
Just that it can be easier…
Notes
Deferred- A proxy for an asynchronous, future event
- Has an interface for getting
resolve()d orreject()ed - Starts in pending state, can only be finished once
- Calls listeners immediately (but always async) once resolved
Promise- Allows listening and state inspection (using state()), but completely immutable so no interface for resolution
- jQuery specific listeners are
done()andfail() - Can be chained with
then()(used to bepipe()) - Can be grouped and processed using
$.when()