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Capture value of Textbox when OnChange is defined in the textbox

I have a dynamically generated grid with x number of textboxes that will be in it. As each textbox is generated, I give it an OnChange event that is a set function.
Html.TextBox(... new { #onchange = "ChangeItemQuantity(" + vm.ID + ", " + fk.id + ")" ...
So when it's rendered, it looks like this:
<input ... type="text" onchange="ChangeItemQuantity(1939, 3)" />
Then, in the script section:
function ChangeItemQuantity(ItemId, ForeignKeyId) {
...
}
In the ChangeItemQuantity() function, how would I also capture the new value of the textbox? I don't really want to use an id on the textbox, because it is part of a grid with many textboxes.
Should I pass it in as a parameter? If so, what would the syntax be of the code that renders the textbox?
Or, is there a way to capture is inside the javascript function?
Thanks!

If you want to store data in the html element why not use data- attributes?
Set them like so
#Html.TextBox(.... new { #class="someClass" data-vmId="vm.ID", data-fkId="fk.id" })
Then set a listener on that class
$('.someClass').change(function() {
var value = $(this).val();
var vmid = $(this).data('vmid');
var fkid = $(this).data('fkid');
}

TextAreaFor doesn't show default value (MVC4)

I want to give my TextAreaFor a default value from my database (a certain comment which they can edit). I use the #Value and I can see it in the html code (inspect element), but in the textarea itself it isn't visible.
My code:
#Html.TextAreaFor(a => a.description, new { Value = ViewBag.Description }
ViewBag.Description = adver.description;

textarea works differently then other input fields in HTML and because of this the value attribute doesn't actually do anything that you'd expect.
<textarea value="you won't see this">you will see this</textarea>
Versus a text field:
<input type="text" value="you will see this" />
Because of this you need to assign the text that you want to be shown in the textarea to the variable before creating the textarea.
Edit
Here's a more complete example for you:
public ActionResult MyAction()
{
var myDefaultDescription = ""; //Replace with whatever you initialize ViewBag.Description with
return View(new AdverModel{ description = myDefaultDescription });
}
This will cause the model to be initialized in the controller. The #Html.TextAreaFor() only uses fields and values from the model object that's passed into the view. The Model variable is read only in the view so you must initialize it in the controller and pass it to the view during the return from the controller.
This will cause that field to auto populate with the default value.

setting the value of textbox equal to address bar in MVC4?

How can I set the Textbox's value equal to address bar?
for example :
localhost:28362/?f=Ava
when we click on a button the value of textbox must set to : Ava
?

Try this, Add Query String Jquery Js(querystring-0.9.0-min.js) in solution
$("#ButtonId").click(function(){
$("#textBoxID").val($.QueryString("f");)
});

Here is Javascript function to get query string value:
function getParameterByName(name) {
name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
var regex = new RegExp("[\\?&]" + name + "=([^&#]*)"),
results = regex.exec(location.search);
return results == null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
}
Then you need to assign this value to a textbox. I would use jQuery:
$(function(){
$("#myTextBoxID").val(getParam("f"));
})

If you want a solution that uses MVC4 rather than JavaScript, define your controller method as:
public ActionResult Index(string f) {
return View(f);
}
In your view, you would then use one of:
#model string;
#Html.TextBoxFor(Model)
or
#model string
<input type='text' value='#Model' name='myValue' />
Obviously this is vastly oversimplified, but should give you a good starting point.

ASP.Net MVC EditorTemplate wrong Id

So I have a double field called Area. I print it this way:
<div>#Html.EditorFor(model => model.Area)</div>
My EditorTemplate for Double looks like this:
#{
var attributes = this.ViewData.ModelMetadata.ContainerType.GetProperty(this.ViewData.ModelMetadata.PropertyName).GetCustomAttributes(true);
var htmlAttributes = GAtec.AgroWeb.Basic.Ux.Web.Helpers.EditorTemplateHelper.GetAllAttributes(ViewData, attributes);
var decimalPlaces = htmlAttributes["data-format"].ToString().Split(',');
var value = decimalPlaces.Length > 1 ? Model.ToString("n" + decimalPlaces[1]) : Model.ToString();
#System.Web.Mvc.Html.InputExtensions.TextBox(this.Html, Html.NameFor(model => model).ToString(), value, htmlAttributes);
}
<script>
$(document).ready(function () {
$("##Html.IdFor(model => model)").restrictNumber();
});
</script>
Nice, but why the html element comes wrong as <input id="Area_Area" /> and the jQuery selector comes right as $("#Area") ?
Both NameFor and IdFor returns "Area" when I watch them on debbuging.
UPDATE:
My htmlAttributes(As #DarinDimitrov asked) returns this array:
["data-min": "0.0", "data-format": "0,2"]

What's the point of stuffing gazilions of inline scripts inside your view (one for each editor template), when you could simply append a class="number" to your input field and then externalize your javascript in a separate file (which is where javascript belongs) and simply use a class selector:
$(document).ready(function () {
$(".number").restrictNumber();
});

#System.Web.Mvc.Html.InputExtensions.TextBox(this.Html, "", value, htmlAttributes);
This resolved my problem. The point is, the MVC knows the model name so you don't have to say him what to print. If you do, it will concat with the model name. But why it does this, I really don't know.

How to Read the value in a hiddenField from javascript

I want to read a value in the hidden field in javascript/Jquery.How can i acheive this ??

try this
var value=$('#HidennfieldID').val()
value will hold the value of hidden field

It's the same as for a regular field:
document.forms[xxx].elements[yyyy].value
xxx is the name of the form, or its number. yyyy is the name of the element (or its number).
You can also use document.getElementById() to get either the form or the field.

Use the field name or id, e.g.
var fVal = $('[name="name"]').val();
var fVal = $('#id').val();

<input type="hidden" value="12345" id="ixd" name='ixd' />
var val = document.getElementById("ixd").value;

This an example to read and write value just with pure javascript.
<input type="hidden" id="field-id" />
<script type="text/javascript">
document.getElementById('field-id').value = "your value which you want to insert";
alert(document.getElementById('field-id').value);
</script>