How to prevent rendering css when loading stylesheet from local storage?

Following problem - I stored a stylesheet in the local storage. But when I try to load it from there I use JSON.parse() and it seems that the browser will already render the CSS. But I would prefer the browser to treat the parsed CSS as text, then append the text to a style tag.

The Code:

loading the stylesheet from server and store it in local storage

function load_css(url){
        $.ajax({
            url: url,
            cache: false,
            dataType: 'text',       
            success: function(res){ 
                $('<style>').attr('id', 'my_style').text(res).prependTo('#my_div');         
                if (typeof(Storage) !== "undefined" && typeof localStorage !== "undefined" && localStorage !== null && typeof localStorage.setItem === 'function') {
                    localStorage.setItem("my_style", JSON.stringify(res));                                  
                }                           
            },
            error: function(err){
                console.log(err);
            }
        }); 
    }

within another function the styles shall be loaded from local storage if set:

try{
    if (typeof(Storage) !== "undefined" && typeof localStorage !== "undefined" && localStorage !== null && localStorage.getItem("my_style") !== null) {
        var css = JSON.parse(localStorage.getItem('my_style'));
        $('<style>').attr('id', 'my_style').text(css).prependTo('#my_div');
        ... //load style from server if local storage not available, item not found

Even when I leave out the line with the created style tag the css is being rendered. With this line I see that if I inspect an element the element styles appear twice in the developer tool bar. So how could I prevent the browser from rendering the styles when using JSON.parse(). Maybe there is another method that treats the styles from local storage as plain text?