Knockout.js - Dynamic columns but limit to a maximum of 5 for each row

Question

I found a similar question/answer here: How to render a table with some fixed and some dynamic columns

But it does not completely solve my problem. I am trying to figure out how I can limit the number of dynamic columns to 5 per row and if there are more than 5 items in the view model, make a new row and repeat for all groups of 5 in the array.

For example:

var vm = {
    item: { name: 'test1' },
    item: { name: 'test2' },
    item: { name: 'test3' },
    item: { name: 'test4' },
    item: { name: 'test5' },
    item: { name: 'test6' }
};

Give that model, how can I get this table?

<table>
   <tr>
      <td>test1</td>
      <td>test2</td>
      <td>test3</td>
      <td>test4</td>
      <td>test5</td>
   </tr>
   <tr>
      <td>test6</td>
   <tr>
</table>

Answer 1

To handle a situation like this, I would probably push the logic into your view model, so that your view can remain simple. So the idea would be to use a dependentObservable to represent your "rows". Then, your view can just foreach through the rows and then foreach through the cells in your row.

Here is a sample that makes that number of columns an observable, so that it can be dynamically updated. http://jsfiddle.net/rniemeyer/9TN9W/

var viewModel = {
    items: ko.observableArray(),
    columnLength: ko.observable(5)  
};

//sample data
for (var i = 0; i < 100; i++) {
    viewModel.items.push({ name: 'test' + i });  
}

//return an array of rows.  Each row is an array of items
viewModel.rows = ko.dependentObservable(function() {
    var result = [],
        colLength = parseInt(this.columnLength(), 10),
        row;


    //loop through items and push each item to a row array that gets pushed to the final result
    for (var i = 0, j = this.items().length; i < j; i++) {
        if (i % colLength === 0) {
            if (row) {
              result.push(row);     
            }
            row = [];
        }
        row.push(this.items()[i]);
    }

    //push the final row  
    if (row) {
        result.push(row);
    }

    return result;
}, viewModel);

Answer 2

The closest I've been able to get to a solution is this:

<table>
    <tbody>
            <tr data-bind="template: { name: 'rowTmpl', foreach: items}">

            </tr>
    </tbody>
</table>
<script id="rowTmpl" type="text/html">

        <td data-bind="text: name"></td>

        <!-- ko if: (vm.items.indexOf($data) + 1) % 5 == 0 -->
        <td>new row html here</td>
        <!-- /ko --> 

</script>


vm = {

            items: ko.observableArray([
                { name: 'test1' }, 
                { name: 'test2' }, 
                { name: 'test3' }, 
                { name: 'test4' }, 
                { name: 'test5' }, 
                { name: 'test6' } 
            ])
        }

        ko.applyBindings(vm);

.. which outputs this:

| test1 | test2 | test3 | test4 | test5 | new row html here | test6 |

This inserts a new element on every 5th item. However, if I substitute <td>new row html here</td> with </tr><tr> the template engine throws an error. Maybe, some other SO-er can build on this and show how to output not strictly correct html.

Anyway, hope this helps a little.