There's a couple of options.

The quick'n'dirty version would be to have your href pass in a query string with the language name, so something like:

<a href='./?lang=sv-SE'>SV</a>

Then in your script you'd see if a query string is passed in and call your function:

if (!String.IsNullOrEmpty(Request.QueryString["lang"]))
{
   var lang = Request.QueryString["lang"];
  // call your function
  ChangeLanguage(lang);
}

In razor you can create a functions area you just for functions like this:

@functions
{
    public void ChangeLanguage(string lang)
    {
        Thread.CurrentThread.CurrentCulture =
           CultureInfo.CreateSpecificCulture(lang);
        Thread.CurrentThread.CurrentUICulture = new
            CultureInfo(lang);

    }
}

You'd want to maybe check the querystring lang is a valid language first.

A nice way would be to maybe use a custom render controller to access the request and change the culture there - see https://our.umbraco.com/Documentation/Reference/Routing/custom-controllers

is working on a reply...