Promise patterns from HTML5Rocks

promises.js

var promise = new Promise(function(resolve, reject) {
  // do a thing, possibly async, then…

  if (/* everything turned out fine */) {
    resolve("Stuff worked!");
  }
  else {
    reject(Error("It broke"));
  }
});


// Like "throw" in plain old JavaScript, it's customary, but not required, to reject with an Error object. 
// The benefit of Error objects is they capture a stack trace, making debugging tools more helpful.
promise.then(function(result) {
  console.log(result); // "Stuff worked!"
}, function(err) {
  console.log(err); // Error: "It broke"
});

// "then" takes two arguments, a callback for a success case, and another for the failure case. 
// Both are optional, so you can add a callback for the success or failure case only.

//Error handling:
get('story.json').then(function(response) {
  console.log("Success!", response);
}, function(error) {
  console.log("Failed!", error);
});

// -OR - 

get('story.json').then(function(response) {
  console.log("Success!", response);
}).catch(function(error) {
  console.log("Failed!", error);
});

// There's nothing special about "catch", it's just sugar for then(undefined, func), but it's more readable. 
// Note that the two code examples above do not behave the same, the latter is equivalent to:

get('story.json').then(function(response) {
  console.log("Success!", response);
}).then(undefined, function(error) {
  console.log("Failed!", error);
});


// http://www.html5rocks.com/en/tutorials/es6/promises/#toc-async