promise chaining in Q and angular $q

promise-chain.js

// find Q/$q implementation
var Q;
try {
   $injector = angular.injector([ 'ng' ]);
   Q = $injector.get('$q');
} catch (err) {
   Q = require('q');
}

// helper function to attach handlers that show how promise is resolved
function attachHandlers(promise, name) {
   promise.then(function(val) {
      console.log('%s resolved as', name, val);
   }).catch(function(err) {
      console.log('%s errored as', name, err);
   });
}

// Chain of 2 promises that resolve successfully
t1 = new Q.defer();
t2 = new Q.defer();
attachHandlers(t1.promise, 't1');
attachHandlers(t2.promise, 't2');
t2.resolve(t1.promise);
t1.resolve(42);

// Chain of 2 promises that resolve unsuccessfully
t1 = new Q.defer();
t2 = new Q.defer();
attachHandlers(t1.promise, 't1');
attachHandlers(t2.promise, 't2');
t2.resolve(t1.promise);
t1.reject('because');