ko.promise

The Problem

In Knockout-based applications of any significant size, you may find yourself writing a lot of the same boilerplate code - wherein you copy the result of a promise into a ko.observable:

var myObservable = ko.observable();
var promiseResult = getSomeResourceAsync();
promiseResult.then(function(value) {
  myObservable(value);
});

This is annoying, error-prone, and becomes unmanageable for complex, asynchronous browser-based applications.

The Solution?

ko.promise attempts to solve this by merging observables and the Promises/A contract. It extends observables with promise-like behavior, allowing the developer to:

• Set up promise pipelines and multi-dependent promises (piggybacking off ko.computed)
• Declaratively write MVVM applications to behave predictably in a totally async progamming model

Basic Example:

We can declare a ko.promise:

var observablePromise = ko.promise(getSomeResourceAsync());

Pipeline it:

var transformedPromise = observablePromise.then(function(value) {
    return value * 2;
});

And bind it:

<div data-bind="
    visible: transformedPromise.loading,
    text: transformedPromise"></div>

Thorough documentation forthcoming :)