aibarra aibarra - 1 year ago 238
Javascript Question

Knockout.Js Array filter syntax

Just getting into javascript and knockout.js. I've found a bunch of examples of what I'm trying to accomplish. And I feel like there is a small syntax error I may be overlooking. I'm trying to filter a set already returned (this.tasks) from a server via ajax/json. I have that working fine. What I would like to do, is have users be able to switch between complete and incomplete tasks.

I switched the code to just run the foreach loop on tasksFiltered. "this.done" is either true or false.

Task template

var taskModel = function(id, title, description, done){
var self = this; = ko.observable(id);
this.title = ko.observable(title);
this.description = ko.observable(description);
this.done = ko.observable(done);

this.showEdit = ko.observable(false);
this.titleUpdate = ko.observable(false);
this.descriptionUpdate = ko.observable(false);

Page Model

var pageModelTasks = function(){
var self = this;
this.task_title = ko.observable("");
this.task_description = ko.observable("");
this.task_title_focus = ko.observable(true);
this.tasks = ko.observableArray([]);

this.tasksFiltered = ko.computed(function() {
return ko.utils.arrayFilter(this.tasks, function(Task) {
return Task.done == true;

// CRUD functions excluded

this doesn't work.

Answer Source

Two minor corrections to your code. First, as @XGreen mentioned, you need to pass the array value, not the observableArray instance, as the first parameter of the arrayFilter function. Lastly, because Task.done is observable, you need to invoke the member to get the value. Here's the modified code:

this.tasksFiltered = ko.computed(function() {
    return ko.utils.arrayFilter(this.tasks(), function(Task) {
        return Task.done() === true;