node.js - Trigger Promise when an event fires -

my entire project uses (bluebird) promises, there's 1 particular library uses eventemitter.

i want achieve like:

promise.on('connect', function() {     x.dosomething(); }).then(function() {     return new promise(function(resolve) {         y.doaction(resolve); // result in `eventb` getting emitted     }); }).on('eventb', function() {     z.handleeventb(); }).then(function() {     z.dosomethingelse(); }); 

i read answer eventemitter in middle of chain of promises. gives me way execute callback 'connect' event. here's have got far

var p = new promise(function(resolve) {     emitter.on('connect', resolve); }); p.on = function() {     emitter.on.apply(emitter, arguments);     return p; }; p.on('connect', function() {     x.dosomething(); }).then(function() {     return new promise(function(resolve) {         y.doaction(resolve); // result in eventb getting emitted     }); }); 

now how chain further 'eventb' ?

i assume want different chain of things each event. if eventb triggered actions of connect, can treat stream of logic.

side note: avoid confusion , else has read codebase, i'd recommend against supplementing promises additional methods unless very thorough documenting them.

from example, seems following work.

var promise = require( 'bluebird' ) var emitter = someemitter() var connected = new promise( function( resolve ){     emitter.on( 'connect', resolve ) })  var eventbhappened = new promise( function( resolve ){     emitter.on( 'eventb', resolve ) })  connected.then( function(){     x.dosomething() }).then( function(){     y.dosomethingelse() // trigger `eventb` })  // promise stream begin once `eventb` has been triggered eventbhappened.then( function(){      z.dosomething() }) 

if you'd simplify constant

var p = new promise( function( resolve ){     emitter.on( 'something', resolve ) }) 

you can use this

function waitforevent( emitter, eventtype ){     return new promise( function( resolve ){         emitter.on( eventtype, resolve )     }) } 

which turns code solution above into

var promise = require( 'bluebird' ) var emitter = someemitter()  function waitforevent( eventemitter, eventtype ){     return new promise( function( resolve ){         eventemitter.on( eventtype, resolve )     }) }  waitforevent( emitter, 'connect' ).then( function(){     x.dosomething() }).then( function(){     y.dosomethingelse() // trigger `eventb` })  // promise stream begin once `eventb` has been triggered waitforevent( emitter, 'eventb' ).then( function(){      z.dosomething() }) 

and because functions in javascript capture scope defined, code further simplified to

var promise = require( 'bluebird' ) var emitter = someemitter()  function waitforevent( type ){     return new promise( function( resolve ){         //emitter has been captured line #2         emitter.on( type, resolve )      }) }  waitforevent( 'connect' ).then( function(){     x.dosomething() }).then( function(){     y.dosomethingelse() // trigger `eventb` })  // promise stream begin once `eventb` has been triggered waitforevent( 'eventb' ).then( function(){      z.dosomething() })