how to access a string variable in the code behind into javascript

In your code behind:

protected string MyString = "This is my string";

Then, in your HTML page:

function GetMyString() {
     return <%= MyString %>
}

You can obviously put the snippet <%= MyString %> where ever you want to use that string. Hoe this helps!

http://stackoverflow.com/questions/9458494/access-c-sharp-variable-from-javascript

http://stackoverflow.com/questions/7555454/access-asp-net-session-variable-from-javascript

You can pass it as JSON object and retrieve it from javascript.