Getting Started with Knockout.js for .NET Developers

Custom functions

Knockout.js allows you to write your own custom functions to extend the capabilities of a standard Knockout.js object. The following objects from the Knockout.js hierarchy can be extended:

• ko.subscribable (root object)
• ko.computed (inherited from ko.subscribable)
• ko.observable (inherited from ko.subscribable)
• ko.observableArray (inherited from ko.observable)

If you write a custom function for an object, the inheritors of the object will also have the written function. For example, you can use a custom function of ko.observable with ko.observableArray.

An example with array filtering

Let's learn how to write a custom function with the following example. We will write the filterByProperty function for ko.observableArray. This function ...