Question

The code is as follows: EmployeeModel is the viewModel and the problem is that when I change an item’s property – deletedFlag in employees (obs array), deletedItems is not updated.

How can i fix this?

  function Employee(data) {
    this.employeid = ko.observable(data.employeid);
    this.name = ko.observable(data.name);
    this.isactive = ko.observable(data.isactive);
    this.deletedFlag = ko.observable(false);
}

var EmployeeModel = function () {
    var self = this;
    self.employees = ko.observableArray([]);

    self.deletedItems = ko.computed(function () {
        return ko.utils.arrayFilter(self.employees(), function (item) {
            return item.deletedFlag == true;
        });
    }, this);
}

EDIT: and the following code marks one item from the array for deletion

self.removeEmployee = function (employee) {
        employee.deletedFlag(true);
    };

Answer 1

The property deletedFlag is an observable, therefore you need to retrieve its current value by invoking it as a function (you cannot compare it directly to any value):

self.deletedItems = ko.computed(function () {
    return ko.utils.arrayFilter(self.employees(), function (item) {
        return item.deletedFlag() == true; // <===
    });
}, this);