Question

In Knockout JS, is it possible to do a foreach that increments by 2? Something similar to:

for (var i = 0; i < array.length; i += 2) {
    // Do stuff
}

The reason I’d like to do this is because the data that I need to loop through is an array rather than an object. Example:

viewModel = function () {
    this.facets = ["Sample", 100, "Sample 2", 200];
}

But the data needs to be displayed like this:

<ul data-bind="foreach: facets"> <!-- Can this foreach be incremented by 2? -->
    <li>$data[$index]: $data[$index + 1]</li>
</ul>

Any help would be greatly appreciated.

Answer 1

You could write a custom binding handler for this but I would rather keep the templates free from such ugly details.

I would recommend writing a ko.computed:

function Model() {
    this.data = ko.observableArray(["Sample", 100, "Sample 2", 200])
    this.items = ko.computed(function() {
        var value = [];
        var data = this.data();
        for (var i=0; i<data.length; i+=2) {
            value.push({ key: data[i], value: data[i+1]);
        }
        return value;
    }, this);
}

var model = new Model();

Now you can iterate over the items in your template and access key and value. Updating the original data array will automatically rebuild the items computed observable.

The template code would look like:

<ul data-bind="foreach: items">
    <li><span data-bind="text: key"></span>: <span data-bind="text: value"></span></li>
</ul>