Protractor_promise.js

var deferred = protractor.promise.defer();
var promise = deferred.promise;

promise.then(function() {
   ...
});

promise.then(function() {
   ...
}).then(function() {
   ...
}).then(null, function() {
   ...
}).then(function() {

}, function() {
   ...
}).then(onSuccess, onFailure);

// success
deferred.fulfill(value);
//failure
deferred.reject(new Error('a problem occurs'));