Question

I’m aware of dynamic script/css loading by adding <style> or <link> tags to head or body of the page, but then it will be executed by browser once downloaded. I was thinking about other ways to download but do not execute javascript/css code. First what comes in my mind was XMLHttpRequest:

//simple execution received script
var executeScript = function(code){
    eval(code);
};
//create XMLHttpRequest in cross-browser manner
var xhr = createXMLHTTPObject();
//check whether file is loaded
var checkStatus = function(){
    if(xhr.readyState  == 4){
        if(xhr.status >= 200 && xhr.status < 300 || xhr == 304){
            executeScript(xhr.responseText);   
        }
        else {//error
        }
    }
};
//do request
xhr.open('get','http://podlipensky.com/examples/dynamicscript/hey.js', true);
xhr.onreadystatechange = checkStatus;
xhr.send(null);

But in this case we’re limited with scripts from the same domain because of the Same Origin Policy (although we can try workaround it with CORS)

Another approach, I was thinking about is to add dynamically iframe to the page and then add script tag to the iframe, so the script will be executed once it downloaded, but it happens in context of another page – iframe.

Are there any other ways to download and not execute the script?

UPDATE:

One of the reasons why it would be useful to download, but not execute javascript/css is to pre-load third-party libraries, but use them only on demand.

Answer 1

You can also use an iframe and use the script/css URL as the src of the frame (so it isn’t evaluated/applied at all), although you’d want to be sure in that case that the JavaScript/CSS was delivered with Content-Type text/plain to avoid unfortunate things happening with < characters and such. Although you should run into SOP issues with this approach as well, on a decent browser, if the iframe src is from a different origin.

Other than that, I think you largely have it covered with the options you list.