Question

This sounds like a trivia question but I really need to know.

If you put the URL of an HTML file in the Location bar of your browser, it will render that HTML. That’s the whole purpose of a browser.

If you give it a JPG, or a SWF, or even PDF, it will do the right things for those datatypes.

But, if you give it the URL of a JavaScript file, it will display the text of that file. What I want is for that file to be executed directly.

Now, I know that if you use the javascript: protocol, it will execute the text of the URL, but that isn’t what I need.

I could have the URL point to an HTML file consisting of a single <script> tag that in turn points to the JavaScript file, but for occult reasons of my own, I cannot do that.

If the file at http://example.com/file.js consists entirely of

 alert("it ran");

And I put that URL in the Location bar, I want “it ran” to pop up as an alert.

I’m skeptical that this is possible but I’m hoping-against-hope that there is a header or a MIME type or something like that that I can set and miraculously make this happen.

Answer 1

This is not possible. The browser has no idea what context the JavaScript should run in; for example, what are the properties of window? If you assume it can come up with some random defaults, what about the behavior of document? If someone does document.body.innerHTML = "foo" what should happen?

JavaScript, unlike images or HTML pages, is dependent on a context in which it runs. That context could be a HTML page, or it could be a Node server environment, or it could even be Windows Scripting Host. But if you just navigate to a URL, the browser has no idea what context it should run the script in.

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As a workaround, perhaps use about:blank as a host page. Then you can insert the script into the document, giving it the appropriate execution context, by pasting the following in your URL bar:

javascript:(function () { var el = document.createElement("script"); el.src = "PUT_URL_HERE"; document.body.appendChild(el); })();