Is it possible to access the MVC ViewBag object from a Javascript file?

Question

Is it possible to do the following from a javascript file in an MVC application?

$(function(){ alert(@ViewBag.someValue); } 

He is currently throwing an error:

reference to undefined xml name @ViewBag

Answer 1

I do not believe that there is currently any way to do this. The Razor engine does not parse Javascript files, but only Razor. However, you can accomplish what you want by setting the variables inside your Razor view:

 <script> var someStringValue = '@(ViewBag.someStringValue)'; var someNumericValue = @(ViewBag.someNumericValue); </script> <!-- "someStringValue" and "someNumericValue" will be available in script --> <script src="js/myscript.js"></script> 

As Joe notes in the comments, the string value above will break if there is one quote in it. If you want to make this completely iron, you will have to replace all single quotes with shielded single quotes. The problem is that all sudden slashes become a problem. For example, if your string is " foo \' bar " and you replace the single quote, then " foo \\' bar " will exit, and you will return to the same problem. (This is the age-related complexity of coded coding). The best way to handle this is to treat backslashes and quotation marks as special ones and make sure they are all escaped:

  @{ var safeStringValue = ViewBag.someStringValue .Replace("\\", "\\\\") .Replace("'", "\\'"); } var someStringValue = '@(safeStringValue)'; 

Answer 2

Not in a JavaScript file, no.
Your JavaScript file may contain a class, and you can instantiate a new instance of this class in the view, then you can pass the ViewBag values ​​in the class constructor.

Or, if it's not a class, your only alternative is to use the data attributes in your HTML elements, assign them to the properties in your view, and get them in a JS file.

Assuming you have this input:

 <input type="text" id="myInput" data-myValue="@ViewBag.MyValue" /> 

Then in your JS file you can get it using:

 var myVal = $("#myInput").data("myValue"); 

Answer 3

To do this, your JavaScript file must be preprocessed on the server side. Essentially, it was supposed to be an ASP.NET view for a certain type, and script tags that reference a file would essentially refer to a controller action that responds to that view.

It is like a can of worms that you do not want to open.

Since JavaScript is client-side, why not just set a value for some element on the client side and associate JavaScript with it. This may be an extra step of indirection, but it sounds much less than a headache than creating a JavaScript view.

Something like that:

 <script type="text/javascript"> var someValue = @ViewBag.someValue </script> 

An external JavaScript file can then reference the JavaScript variable someValue within the scope of this document.

Or even:

 <input type="hidden" id="someValue" value="@ViewBag.someValue" /> 

Then you can access this hidden input.

Unless you come up with some really smooth way to make your JavaScript file usable as a presentation. This is certainly doable, and I can't readily think of any problems you would have (other than the really ugly view code, since the view mechanism will be very confused as to what JavaScript is and what Razor is .. so expect a ton <text> markup), so if you find a smooth way to do this, it will be pretty cool, although perhaps not intuitive for someone who needs code support later.

Answer 4

in html:

 <input type="hidden" id="customInput" data-value = "@ViewBag.CustomValue" /> 

in Script:

 var customVal = $("#customInput").data("value"); 

Answer 5

Use this code in the .cshtml file.

  @{ var jss = new System.Web.Script.Serialization.JavaScriptSerializer(); var val = jss.Serialize(ViewBag.somevalue); } <script> $(function () { var val = '@Html.Raw(val)'; var obj = $.parseJSON(val); console.log(0bj); }); </script> 

Answer 6

Create a view and return it as a partial view:

 public class AssetsController : Controller { protected void SetMIME(string mimeType) { this.Response.AddHeader("Content-Type", mimeType); this.Response.ContentType = mimeType; } // this will render a view as a Javascript file public ActionResult GlobalJS() { this.SetMIME("text/javascript"); return PartialView(); } } 

Then, in the GlobalJS view, add javascript code, for example (adding // will make visual studio intellisense read like a java script)

 //<script> $(document).ready(function () { alert('@ViewBag.PropertyName'); }); //</script> 

Then in your last view, you can add a javascript link that way.

 <script src="@Url.Action("GlobalJS", "Assets")"></script> 

Then in your final controller you can create / pass your ViewBags and it will be displayed in your javascript.

 public class MyFinalViewController : Controller { public ActionResult Index() { ViewBag.PropertyName = "My ViewBag value!"; return View(); } } 

Hope this helps.

Answer 7

I noticed that the Visual Studio built-in error detector gets dumb if you try to do this:

 var intvar = @(ViewBag.someNumericValue); 

Because @ (ViewBag.someNumericValue) can evaluate to zero, which will lead to the creation of the following invalid JavaScript:

 var intvar = ; 

If you are sure that someNemericValue will be set to a valid numeric data type, you can avoid the presence of Visual Studio warnings by following these steps:

 var intvar = Number(@(ViewBag.someNumericValue)); 

This can generate the following example:

 var intvar = Number(25.4); 

And it works for negative numbers. In case the item is not in your view bag, Number () takes the value 0.

More Visual Studio alerts! But make sure that the value is set and is numeric, otherwise you will open the door for possible JavaScript injection attacks or runtime errors.

Answer 8

In the action of the controllers add:

  public ActionResult Index() { try { int a, b, c; a = 2; b = 2; c = a / b; ViewBag.ShowMessage = false; } catch (Exception e) { ViewBag.ShowMessage = true; ViewBag.data = e.Message.ToString(); } return View(); // return View(); } in Index.cshtml Place at the bottom: <input type="hidden" value="@ViewBag.data" id="hdnFlag" /> @if (ViewBag.ShowMessage) { <script type="text/javascript"> var h1 = document.getElementById('hdnFlag'); alert(h1.value); </script> <div class="message-box">Some Message here</div> }