How to create a computed observable array in Knockout

Question

I would like to know how to create a computed observable array.

In my view model, I have 2 observable arrays, and I would like to have a computed observable array

Answer 1

I know this is an old question but I thought I'd throw my answer in there:

var u = ko.utils.unwrapObservable;

ko.observableArray.fn.filter = function (predicate) {
    var target = this;

    var computed = ko.computed(function () {
        return ko.utils.arrayFilter(target(), predicate);
    });

    var observableArray = new ko.observableArray(u(computed));

    computed.subscribe(function (newValue) { observableArray(newValue); });

    return observableArray;
};