Promises and Callbacks

callback-execution.js

'use strict';

var TestConstructor = require('./test-module');

var Testing = new TestConstructor();

Testing.doSomething(function(err, data) {
  // oh im done. an async process has happened
});

promise-execution.js

'use strict';

var TestConstructor = require('./test-module');

var Testing = new TestConstructor();

Testing.doSomething()
  .then(function(data) {
    // oh im done. an async process was successful
  })
  .catch(function(err) {
    // oh shit, something went wrong
  })
  .then(function(data) {
    // do something else, which would usually go in a callback
  });

promise-setup.js

var Promise = (typeof Promise === 'undefined') ? require('bluebird') : Promise;

test-module-with-promises.js

'use strict';

var Test = function() {};

Test.prototype.doSomething = function(callback) {
  // set up
  
  // do some more stuff
  
  // lets execute the callback
  if(typeof callback === 'function') {
    return this.asyncProcess(callback);
  }
  
  // whoops, no callback. assume promises
  return new Promise(function(resolve, reject) {
    this.asyncProcess(function() {
      if(err) {
        return reject(err);
      }
      resolve(data);
    });
  }.bind(this));
};

module.exports = Test;

test-module.js

'use strict';

var Test = function() {};

Test.prototype.doSomething = function(callback) {
  // set up
  
  // do some more stuff
  
  // execute an async function, which will then
  // call your callback when done
  this.asyncProcess(callback);
};

module.exports = Test;