Possible to access MVC ViewBag object from Javascript file

Question

Is it possible to do the following from a javascript file in an MVC application     function       alert  ViewBag someValue       Currently it throws the error      reference to undefined XML name  ViewBag

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I noticed that Visual Studio s built-in error detector kind of gets goofy if you try to do this   var intvar     ViewBag someNumericValue     Because   ViewBag someNumericValue  has the potential to evaluate to nothing  which would lead to the following erroneous JavaScript being generated   var intvar       If you re certain that someNemericValue will be set to a valid numeric data type  you can avoid having Visual Studio warnings by doing the following   var intvar   Number   ViewBag someNumericValue      This might generate the following sample   var intvar   Number 25 4     And it works for negative numbers  In the event that the item isn t in your viewbag  Number   evaluates to 0   No more Visual Studio warnings  But make sure the value is set and is numeric  otherwise you re opening doors to possible JavaScript injection attacks or run time errors

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In controllers action 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    lt input type  hidden  value   ViewBag data  id  hdnFlag    gt    if  ViewBag ShowMessage         lt script type  text javascript  gt           var h1   document getElementById  hdnFlag             alert h1 value         lt  script gt       lt div class  message-box  gt Some Message here lt  div gt

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I don t believe there s currently any way to do this   The Razor engine does not parse Javascript files  only Razor views   However  you can accomplish what you want by setting the variables inside your Razor view    lt script gt    var someStringValue      ViewBag someStringValue      var someNumericValue     ViewBag someNumericValue    lt  script gt   lt  --  someStringValue  and  someNumericValue  will be available in script -- gt   lt script src  js myscript js  gt  lt  script gt    As Joe points out in the comments  the string value above will break if there s a single quote in it   If you want to make this completely iron-clad  you ll have to replace all single quotes with escaped single quotes   The problem there is that all of the sudden slashes become an issue   For example  if your string is  foo    bar   and you replace the single quote  what will come out is  foo     bar   and you re right back to the same problem    This is the age old difficulty of chained encoding    The best way to handle this is to treat backslashes and quotes as special and make sure they re all escaped              var safeStringValue   ViewBag someStringValue            Replace                          Replace                    var someStringValue      safeStringValue

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For CoreMVC 3 1  that would be   using Newtonsoft Json var listInJs     Html Raw JsonConvert SerializeObject ViewBag SomeGenericList

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in Html    lt input type  hidden  id  customInput  data-value     ViewBag CustomValue    gt    in Script   var customVal       customInput   data  value

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In order to do this your JavaScript file would need to be pre-processed on the server side   Essentially  it would have to become an ASP NET View of some kind  and script tags which reference the file would essentially be referencing a controller action which responds with that view   That sounds like a can of worms you don t want to open   Since JavaScript is client-side  why not just set the value to some client-side element and have the JavaScript interact with that   It s perhaps an additional step of indirection  but it sounds like much less of a headache than creating a JavaScript view   Something like this    lt script type  text javascript  gt      var someValue    ViewBag someValue  lt  script gt    Then the external JavaScript file can reference the someValue JavaScript variable within the scope of that document   Or even    lt input type  hidden  id  someValue  value   ViewBag someValue    gt    Then you can access that hidden input   Unless you come up with some really slick way to actually make your JavaScript file usable as a view   It s certainly doable  and I can t readily think of any problems you d have  other than really ugly view code since the view engine will get very confused as to what s JavaScript and what s Razor    so expect a ton of  lt text gt  markup   so if you find a slick way to do it that would be pretty cool  albeit perhaps unintuitive to someone who needs to support the code later

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Not in a JavaScript file  no  Your JavaScript file could contains a class and you could instantiate a new instance of that class in the View  then you can pass ViewBag values in the class constructor   Or if it s not a class  your only other alternative  is to use data attributes in your HTML elements  assign them to properties in your View and retrieve them in the JS file    Assuming you had this input    lt input type  text  id  myInput  data-myValue   ViewBag MyValue    gt    Then in your JS file you could get it by using   var myVal       myInput   data  myValue

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Use this code in your  cshtml file           var jss   new System Web Script Serialization JavaScriptSerializer        var val   jss Serialize ViewBag somevalue                lt script gt            function                  var val     Html Raw val                var obj     parseJSON val               console log 0bj                lt  script gt

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onclick  quot myFunction   ViewBag MyValue   quot

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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 the javascript code like  adding the    will make visual studio intellisense read it as java-script      lt script gt         document  ready function             alert   ViewBag PropertyName                 lt  script gt    Then in your final view you can add a reference to the javascript just like this    lt script src   Url Action  GlobalJS    Assets    gt  lt  script gt     Then in your final view controller you can create pass your ViewBags and it will be rendered in your javascript   public class MyFinalViewController   Controller       public ActionResult Index                 ViewBag PropertyName    My ViewBag value            return View              Hope it helps

[c#] Possible to access MVC ViewBag object from Javascript file?

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