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Is It The Last `script` Element The Currently Running Script?

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Is it safe to assume that the last script element* in the document when the script runs** is the currently running script? For example, I want to create a script that can be droppe

Solution 1:

It's not an absolute guarantee no. Check out this JSFiddle: http://jsfiddle.net/jAsek/

<!DOCTYPE html><title>Test case</title><div><p>At the start</p><scriptid="first">var scr1 = document.createElement("script");
        scr1.setAttribute("id", "early");
        document.body.appendChild(scr1);
    </script><p>After the first script</p><scriptid="second">functiongetCurrentScriptElement() {
            var scripts = document.getElementsByTagName('script');
            return scripts[scripts.length - 1];
        }

        alert(getCurrentScriptElement().id);
    </script><p>At the end</p></div>

Here the alert reports the id of the injected script "early", not the id of currently running script "second".

There's no practical difference between internal and external scripts.

Solution 2:

I don’t think it’s a safe assumption at all, as browsers execute javascript code quite differently depending on a number of things (like if you have other script elements in the head, if they are external etc.).

You should just require people to use a dummy element with a custom id or class. That way you will also make it possible to do whatever you do multiple times a page without having to run the script multiple times.

This is also what is done when using widgets, for example Google’s +1 button.

An alternative would be to use document.write to write additional content while the script is executed. This will not replace the script tag however, but simply add something after it.

Solution 3:

You probably want to use document.currentScript that is currently supported by 90% of browsers and fallback to document.scripts[document.scripts.length-1] if you're targetting IE 

functionwriteHere(element)
{
 var sc = document.currentScript || document.scripts[document.scripts.length-1] ;  
 sc.parentNode.insertBefore(element, sc);
 // or in jquery $(sc).before($(element));
}

note: I didn't test document.scripts[document.scripts.length-1] thoroughly but it should work in most cases (but not in Alohci exemple). And this is a fix for IE so who cares :)

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