knockout.js - Error when using KnockoutObservableArray in TypeScript -

i have 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         });         //return         })     } 

but when load page, javascript error, says, typeerror: _this.projects not function index-viewmodel_test.js

the rendered javascript part is,

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

what missing here?

the problem projects member not yet defined when filteredlist computed. moving computation in constructor of class solved issue. code:

constructor() {         this.projects = ko.observablearray<project>([]);         this.filteredlist = ko.computed(() => {             var elements = ko.utils.arrayfilter(this.projects(), (item: project) => {                 //return             });             //return         });     }