Using Knockout to Populate Bootstrap Rows and Span

Question

Well essentially I'm trying to populate a Bootstrap template via Knockout and a JSON object.

Bootstrap scaffolding:

<div class="row-fluid">
    <div class="span4">
        <h1>App Title</h1>
        <p>App Description</p>
    </div>
    <div class="span4">
        <h1>App Title</h1>
        <p>App Description</p>
    </div>
    <div class="span4">
        <h1>App Title</h1>
        <p>App Description</p>
    </div>
</div>
<div class="row-fluid">
    <div class="span4">
        <h1>App Title</h1>
        <p>App Description</p>
    </div>
    <div class="span4">
        <h1>App Title</h1>
        <p>App Description</p>
    </div>
    <div class="span4">
        <h1>App Title</h1>
        <p>App Description</p>
    </div>
</div>
...

Here is the Knockout code we're using:

var viewModel;

$.get('AppData.json', function (data) {
    jsonData = $.parseJSON(data);
    viewModel = ko.mapping.fromJS(jsonData);
    var apps = viewModel.Apps();
    ko.applyBindings(viewModel);
});

The problem is that I cannot get Knockout to inject the </div><div class="row-fluid"> required after running a knockout conditional of index modulo 3... I'm assuming because those <div> tags are dangling / not closed.

In short, how do I get viewModel.Apps();'s array of objects to fit within the above Bootstrap scaffolding?

Answer 1

Make a computed observable which slices apps observable/observable array into arrays of three elements, and then bind some root element to it with foreach binding. Something like this.

Observable:

viewModel.appRows = ko.computed(function() {
    var apps = this.Apps();
    var result = [];
    for (var i = 0; i < apps.length; i += 3) {
        var row = [];
        for (var j = 0; j < 3; ++j) {
            if (apps[i + j]) {
                row.push(apps[i + j]);
            }
        }
        result.push(row);
    }
    return result;
}, viewModel);

Markup:

<div class="container" data-bind="foreach: appRows">
    <div class="row-fluid" data-bind="foreach: $data">
        <div class="span4">
            <h1 data-bind="text: title"></h1>
            <p data-bind="text: description"></p>
        </div>
    </div>
</div>

Answer 2

I´m using bootstrap3 and wanted to have x objects per row, where x is depending on the window size e.g on the col class.

e.g i have elements with class :

col-lg-2 col-md-2 col-sm-3 col-xs-4

so

if xs then a row has 3 items

if lg then a row has 6 items ...

I extended the answer of rkhayrov to put it to work

/* determine the current bootstrap environment */
function findBootstrapEnvironment() {
    var envs = ['xs', 'sm', 'md', 'lg'];

    $el = $('<div>');
    $el.appendTo($('body'));

    for (var i = envs.length - 1; i >= 0; i--) {
        var env = envs[i];

        $el.addClass('hidden-'+env);
        if ($el.is(':hidden')) {
            $el.remove();
            return env
        }
    };
}


/* determine How many objs per row */
function determineObjectsPerRow(){
    switch(findBootstrapEnvironment()) {
        case 'xs':
            return 3;
            break;
        case 'sm':
            return 4;
            break;
        case 'md':
            return 6;
            break;
        case 'lg':
            return 6;
            break;
    }
}


        var objsPerRow= determineObjectsPerRow();

        for (var i = 0; i < apps.length; i += objsPerRow) {
            var row = [];
            for (var j = 0; j < objsPerRow; ++j) {
                if (apps[i + j]) {
                    row.push(apps[i + j]);
                }
            }
            result.push(row);
        }

i added a dependency to width and height, which are observables So the functions will be recomputed if window is resized

var base = {
    AppModel:function (data) {
        var self = this;
        self.data = ko.observable({
            documents:ko.observableArray([]),
            width:ko.observable($(window).width()),
            height:ko.observable($(window).height())
        });

        /* calculate rows based on bootstrap environment */
        self.appRows = ko.computed(function() {
            self.data().height();
            self.data().width();
            var apps = self.data().documents();
            var result = [];
            var objsPerRow= determineObjectsPerRow();

            for (var i = 0; i < apps.length; i += objsPerRow) {
                var row = [];
                for (var j = 0; j < objsPerRow; ++j) {
                    if (apps[i + j]) {
                        row.push(apps[i + j]);
                    }
                }
                result.push(row);
            }
            return result;
        }, self); 

    },
};

and the resize handler

$(window).resize(function(event) {
    vm.data().height($(window).height());
    vm.data().width($(window).width());
});

it just works like a Charme, the rows are generated nicely for each device-width

i leave it here if anyone needs to achieve the same

Answer 3

I had to solve a very similar problem myself: rendering bootstrap grids with an observable array but with bootstrap v3 and ko v3.0. I'll leave my solution here for future reference.

I'm using a plain function instead of a computed one, since binding are implemented using them by default (see RP Niemeyer answer here https://stackoverflow.com/a/6712389/323751)

In my View Model:

this.partitioned = function (observableArray, count) {
    var rows, partIdx, i, j, arr;

    arr = observableArray();

    rows = [];
    for (i = 0, partIdx = 0; i < arr.length; i += count, partIdx += 1) {
        rows[partIdx] = [];
        for (j = 0; j < count; j += 1) {
            if (i + j >= arr.length) {
                break;
            }
            rows[partIdx].push(arr[i + j]);
        }
    }
    return rows;
};

Template:

<div data-bind="foreach: partitioned(userProjects, 3)">
  <div class="row"
       data-bind="template: { name: 'projectCell', foreach: $data }"></div>
</div>

<script id="projectCell" type="text/html">
  <div class="col-md-4" data-bind="text: name"></div>
</script>

Hope somebody find this useful.