How to call JavaScript function from MVC controller action?

 To call a JavaScript function from an MVC controller action, you can use the ViewBag object to store the function name or any data that you need to pass to the JavaScript function, and then use a view to call the JavaScript function.

Here's an example:

1. Define the JavaScript function in your view:

<script>
function myFunction(data) {
  alert("Data received: " + data);
}
</script>

2. In your controller action, set the ViewBag object with the function name and any data that you need to pass to the function:

public ActionResult MyAction()
{
    ViewBag.FunctionName = "myFunction";
    ViewBag.Data = "Hello from the controller!";
    return View();
}

3. In your view, call the JavaScript function using the ViewBag object:

<script>
if ('@ViewBag.FunctionName' !== '') {
  window['@ViewBag.FunctionName']('@ViewBag.Data');
}
</script>

In this example, the JavaScript function myFunction is called in the view using the ViewBag object. The if statement checks to see if the function name is not empty, and if it is not empty, it calls the function with the data passed as an argument.

Note that the window object is used to call the function, and the @ symbol is used to escape the Razor syntax so that the ViewBag object is properly rendered as a string in the JavaScript code.

This is just one example of how you can call a JavaScript function from an MVC controller action. The specific approach may vary depending on your requirements and the structure of your application.