Asynchronous JS with Promise

Transcript

1. Asynchronous JS with Promise 王浩宇 Makara Wang makara@wiredcraft.com 2013.02.23
2. JS Asynchronous, sometimes not Event driven, sometimes not
3. Promise http://wiki.commonjs.org/wiki/Promises/A An (eventual) value 3 states: unfulfilled, fulfilled, and failed
4. Implementations jQuery Dojo Q - https://github.com/kriskowal/q When.js - https://github.com/cujojs/when Deferred - https://github.com/medikoo/ deferred
5. Example with Deferred Load a Backbone.js model Perform some operations Error handling
6. function fetch(model) { var def = deferred(); model.fetch({ success: function(model) { def.resolve(model); }, error: function() { def.resolve(new Error('lorem')); } }); return def.promise; }
7. deferred(new Model({id: 1})) .then(fetch) .then(function(model) { // ... }) // Or .end() .then(function() { // ... }, function(err) { // ... });
8. Compare with Async Async - https://github.com/caolan/async Think in data Examples: user login
9. async.waterfall([ function(callback) { // Load a user model. callback(null, user); }, function(user, callback) { // Call the login API. user.login({ success: function() { user.authenticated = true; callback(null, user); }, error: function() { callback(new Error('lorem')); } }); } ], function(err, user) {});
10. // Or simply name it `login` function getLoggedInUser(user) { var def = deferred(); // Call the login API. user.login({ success: function() { user.authenticated = true; def.resolve(user); }, error: function() { def.resolve(new Error('lorem')); } }); return def.promise; }
11. Work with Express.js app.get('/', function(req, res, next) { // This returns a promise. loadSomething(x).end(function(data) { res.send(y); // Or req.y = data; next(); }, next); });
12. Deferred https://github.com/medikoo/deferred http://www.medikoo.com/asynchronous- javascript
13. Thanks! Questions?