Why can not I concat data to observable array in knockout

Question

I am trying to add elements from the server to observable array in knockout.

Here is my ViewModel:

function ArticlesViewModel() {
    var self                = this;
    this.listOfReports      = ko.observableArray([]);

    self.loadReports = function() {
        $.get('/router.php', {type: 'getReports'}, function(data){
            for (var i = 0, len = data.length; i < len; i++){
                self.listOfReports.push(data[i]);
            }
        }, 'json');
    };

    self.loadReports();
};

And it works perfectly. But I know that I can merge two arrays in javascript using concat() and as far as I know concat works in knockout. So when I try to substitute my for loop with self.listOfReports().concat(data); or self.listOfReports.concat(data); , nothing appears on the screen.

In the first case there is no error, in the second error tells me that there is no method concat.

So how can I concat the data without my loop. And I would be really happy to hear why my method was not working

Answer 1

The observableArray does not support the concat method. See the documentation for the officially supported array manipulation methods.

However what you can do is to call concat on the underlying array and then reassign this the new concatenated array to your observable:

self.listOfReports(self.listOfReports().concat(data));

The linked example works because the self.Products().concat(self.Products2()) were used in a loop. If you just write self.listOfReports().concat(data); it still concatenates but you just thrown away the result and don't store it anywhere, that is why you need to store it back to your observableArray.