Error when using KnockoutObservableArray in TypeScript

Question

I have the following code:

class IndexViewModel {
    projects: KnockoutObservableArray<Project>;

    constructor() {
        this.projects = ko.observableArray<Project>([]);
    }

    filteredList: KnockoutComputed<Project[]> = ko.computed(() => {
        var elements = ko.utils.arrayFilter(this.projects(), (item: Project) => {
           //do something
        });
        //return something
        })
    }

But when I load the page, I get a JavaScript error, that says, TypeError: _this.projects is not a function index-ViewModel_test.js

The rendered JavaScript for that part is,

this.filteredList = ko.computed(function () {
            var elements = ko.utils.arrayFilter(_this.projects(), function (item) {
                //return something
            });
            //return something
        })

What am I missing here?

Silviu Preda · Accepted Answer · 2015-07-23 13:05:59Z

1

The problem was that the projects member was not yet defined when the filteredList was computed. Moving the computation in the constructor of the class solved my issue. The code:

constructor() {
        this.projects = ko.observableArray<Project>([]);
        this.filteredList = ko.computed(() => {
            var elements = ko.utils.arrayFilter(this.projects(), (item: Project) => {
                //return something
            });
            //return something
        });
    }

edited Jul 23, 2015 at 13:05

answered Jul 23, 2015 at 10:33

Silviu Preda

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