ASP.NET MVC 3 HiddenFor Javascript

Question

I have two hidden input fields in my form:

<input type="hidden" name="lat" id="lat" value=""/>
<input type="hidden" name="long" id="long" value="" />

I am assigning their value by doing the following:

document.getElementById('lat').value = lat;
document.getElementById('long').value = lng;

Can someone please tell me how I can remove the hidden <input> fields and replace them with a @Html.HiddenFor<> and make my Javascript update the HiddenFor? I want to do this because it will obviously automatically bind the data.

My HiddenFor currently looks something like this:

@Html.HiddenFor(m => Model.Listing.Location.Latitude);
@Html.HiddenFor(m => Model.Listing.Location.Longitude);

I change the Javascript to do this:

document.getElementById('Listing.Location.Latitude').value = lat;
document.getElementById('Listing.Location.Longitude').value = lng;

I get the following error in the Console:

Uncaught TypeError: Cannot set property 'value' of null 

Can anyone see where I am going horribly wrong?

Answer 1

The Ids of these fields will have underscores not dots, their names will have the dots. Try this:

document.getElementById('Listing_Location_Latitude').value = lat;

Answer 2

Try this.

@Html.HiddenFor(m => m.Listing.Location.Latitude, new {id = "theIdyouWant"})

So you can get the element using Javascript:

document.getElementById("theIdyouWant")