This document discusses promises in JavaScript. Promises provide a way to work with asynchronous operations in a cleaner way. A promise returns an object that represents the eventual result of an asynchronous operation. Promises can have states of pending, fulfilled, or rejected. Promises allow for chaining of callbacks and make error handling easier when working with asynchronous code. The document provides examples of using promises with jQuery's deferred object implementation.

1. PROMISES IN
JAVASCRIPT

2. ABOUT ME
Rubyist / JavaScripter
Yeoman team member
http://blog.revathskumar.com
Twitter/Github - @revathskumar

3. WHAT ARE PROMISES?
A pattern to work with asyncronous operations much neatly.
A function return a object called promise, which is the eventual
result of the operation.
operated via then method.
States : Pending / Fulfilled / Rejected
poiete(nufle,oRjce)
rms.hnoFlild neetd

4. WHY WE NEED PROMISES?
Chaining
Attach multiple
callbacks
Pool operations
Easy error handling

5. Ue.e(,
srgt1{
sces fnto({
ucs: ucin)
cnoelg'ucs';
osl.o(Sces)
}
,
err fnto({
ro: ucin)
cnoelg'ro';
osl.o(Err)
}
}
)

6. IN PROMISE
Ue.e()te(
srgt1.hn
fnto({
ucin)
cnoelg'ucs';
osl.o(Sces)
}
,
fnto({
ucin)
cnoelg'ro';
osl.o(Err)
}
)
;

7. Ue.e(1,{
srgt''
sces fnto({
ucs: ucin)
Acut.e(1,{
consgt''
sces fnto({
ucs: ucin)
Acut.pae{wte:@dysai,{
consudt(titr adomn}
sces fcto({
ucs: unin)
cnoelg'ucs'
osl.o(Sces)
}
,
err fnto({
ro: ucin)
cnoelg'ro';
osl.o(Err)
}
}
)
}
,
err fcto({
ro: unin)
cnoelg'ro';
osl.o(Err)
}
}
)
}
,
err fnto({
ro: ucin)
cnoelg'ro';
osl.o(err)
}
};
)

8. Ue.e()
srgt1
.hnAcut.e)
te(consgt
.hnfnto({
te(ucin)
rtr Acut.pae{wte:@dysai)
eun consudt(titr adomn}
}
)
.hnfnto({
te(ucin)
cnoelg'ucs';
osl.o(Sces)
}
)
.hnudfnd fnto({
te(neie, ucin)
cnoelg'ro';
osl.o(Err)
};
)
vrUe =(ucin)
a sr
fnto({
fnto gtue_d{
ucin e(sri)
vrpoie=nwAls)
a rms
e pu(;
$gt'ues'+ue_d {
.e(/sr/
sri,
sces fnto(aa{
ucs: ucindt)
poieflildt.con_d;
rms.ufl(aaacuti)
}
,
err fnto({
ro: ucin)
poierjc(Err)
rms.eet'ro';
}
};
)
rtr poie
eun rms;
}
rtr {
eun
gt gt
e: e
}
}
)

9. POOLING
Alspo(
pu.ol
aycuc)
snFn(,
aohrsnFn(
nteAycuc)
)
.hnaycucs,aycro)
te(snSces snErr;

10. USING JQUERY
$we(
.hn
$aa("pg1pp )
.jx /ae.h" ,
$aa("pg2pp )
.jx /ae.h" ,
)
.hnoSces oErr;
te(nucs, nro)

11. JQUERY : MULTIPLE CALLBACKS
$we(ucin)
.hnfnto({
cnoelg'el Poie)
osl.o(Hlo rms';
}
)
.hnfnto({
te(ucin)
cnoelg'ucs1)
osl.o(Sces';
} fnto({
, ucin)
cnoelg'ro1)
osl.o(Err';
}
)
.hnfnto({
te(ucin)
cnoelg'ucs2)
osl.o(Sces';
} fnto({
, ucin)
cnoelg'ro2)
osl.o(Err';
};
)

12. REFERENCE
1.
2.
3.
4.
http://promises-aplus.github.io/promises-spec/
http://wiki.commonjs.org/wiki/Promises/A
https://github.com/rhysbrettbowen/Aplus/
http://api.jquery.com/category/deferred-object/