How do I give JavaScript variables data from ASP.NET variables?

Question

I have created a SCORM API for our LMS and right now I am using hard coded userID and courseID variables (variables that reference things in the database). I need to pass th

Answer 1

This article describes the most pragmatic solution several pragmatic solutions to your problem.

Answer 2

Probably best easiest to expose them as properties of your page (or master page if used on every page) and reference them via page directives.

 <script type="text/javascript">
     var userID = '<%= UserID %>';
     var courseID = '<%= CourseID %>';

     .... more stuff....
 </script>

Then set the values on Page_Load (or in the Page_Load for the master page).

  public void Page_Load( object source, EventArgs e )
  {

        UserID = Session["userID"];
        CourseID = Session["courseID"];
        ...
  }

Answer 3

@tvanfosson's answer is how I have normally done this in the past, but was just trying to think of something a bit more elegant. Thought I'd throw this out there.

You can set up a HashTable in the codebehind and also initialize a JavaScriptSerializer:

Protected json As New System.Web.Script.Serialization.JavaScriptSerializer
Protected jsvars As New Hashtable

Then set variables like this:

jsvars.Add("name", "value")

Then serialize the variables into JavaScript in your page:

<script type="text/javascript">
    var vars = <%=json.Serialize(jsvars)%>;
    alert(vars.name);
</script>

This ensures that all variables are properly escaped and also minimizes the code if you need to work with a lot of variables.

Answer 4

I'm not sure about SCORM or .ashx files (no experience there) but as far as getting values from ASP.NET you can do all sorts of things like

var xyz = '<%= variable %>';

from within your ASP.NET page. There are various ways to accomplish this but the end result is that the ASP.NET page renders the values of the variable in the HTML (or JavaScript) that is sent to the browser.

This is a generic ASP.NET and JavaScript answer, there may be a more elegant solution out there for you.

Answer 5

All the answers here that suggest something like

var userID = '<%= UserID %>';

are all missing something important if the variable you are embedded can contain arbitrary string data. The embedded string data needs to be escaped so that if it contains backslashes, quotes or unprintable characters they don't cause your Javascript to error.

Rick Strahl has some suggestions for the escaping code needed here. Using Rick's code the embedded variable will look like this:

var userId = <%= EncodeJsString(UserID) %>;

Note that there are no quotes now, Rick's code wraps the escaped string with quotes.

Answer 6

Here are the steps that you will have to take:

In your code behind page:

private int _userId;
private int _courseId;
protected int CourseId
{
  get { return _courseId;}
  set { _courseId = value;}
}
protected int UserId
{
 get { return _userId;}

set { _userId = value;}
}

Step 2 : based on your requirement now you have to set up those properties. The catch is that these properties should be set before they are referenced from the JavaScript. Maybe something like this in the Page_Load event:

_userId = Session["userId"];
_courseId = Request.QueryString["CourseId"] != null ? Request.QueryString["CourseId"] : String.empty;

Of course you can parse them to appropriate types based on your requirements.

Finally, you can reference them in JavaScript as follows:

var currentUserId = '<% = UserId %>';
var currentCouseId = '<% = CourseId %>';

This should definitely work. I have used this approach many times.