Setting TabIndex in Knockout

Question

I need to set tabindex to the dynamically generated controls using knockout. I databind the attributes in UI level, but it seems not working. Following is the HTML code for the databinding:

  <tbody data-bind="foreach: Week1">
                            <tr class="formFields" style="vertical-align: top;">
                                <td class="formFields" width="8%" data-bind="text: Day">
                                </td>
                                <td class="formFields" width="5%" align="center">
                                    <select class="combobox" data-bind="value:Required, attr:{tabindex: 42 + Date + $index()}" >
                                        <option value="E">Eligible</option>
                                        <option value="O">On</option>
                                        <option value="F">Off</option>
                                    </select>
                                </td>
                                <td class="formFields" width="10%" align="center" >
                                   <input class="txtbox"  type="text" placeholder="S:" data-bind="value:SetupTime, attr: { tabindex: 43 + Date + $index() }/>
                                   <input class="txtbox"  type="text" placeholder="R:" data-bind="value:CloseTime, attr: { tabindex: 44 + Date + $index() }" />
                                </td>
                                <td class="formFields" width="10%" align="center">
                                   <input class="txtbox" type="text" placeholder="Min:" data-bind="value:MinHrsPerDay, attr: { title:  tabindex: 45 + Date + $index() }"/>
                                   <input class="txtbox" type="text" placeholder="Max:" data-bind="value:MaxHrsPerDay, attr: { title: tabindex: 46 + Date + $index() }"/>
                                </td>
                                <td class="formFields" width="6%" align="center">
                                    <input class="txtbox" align="middle" type="text" data-bind="value:MinWorkShift, attr: { tabindex: 47 + Date + $index()  }"/>
                                </td>
                                </tr>
                            </tbody>

Here Date is a property of my viewmodel which represents days as 0-6. Since there can be multiple rows, I'm using $index() to calculate the tab index of the control in each row.

But this is what I see at runtime:

<input type="text" data-bind="value:SetupTime, attr: {  tabindex: 43 + Date + $index() }" placeholder="S:"  class="txtbox" tabindex="43function d(){if(0&lt;arguments.length){if(!d.equalityComparer||!d.equalityComparer(c,arguments[0]))d.H(),c=arguments[0],d.G();return this}b.r.Wa(d);return c}2">

Could someone please help me correct this?

Thanks in Advance

Answer 1

Because your Date property is an ko.observable so you need to get its value by calling it as a function, so with Date().

So you need to change your bindings to:

data-bind="value:SetupTime, attr: {  tabindex: 43 + Date() + $index() }" 

You only need to call it with Date() if you are usign your observable inside an expression like 43 + Date() + $index() (note the () also after the $index.)

If you directly binding to an observable then you don't need the () like in the data-bind="value:Required", because in this case KO will automatically "unwraps" the value for you.