Can JavaScript access source code of a <script src=""> element?

Question

<script id="s1" src="foo.js"></script>
<script>
    alert('foo.js contains' + _source_code_of('s1'))
</script>

Can _source_code_of be implemented?

Answer 1

No, this would allow to retrieve the contents of any URL, which would break some security policies. (This would be an equivalent of an ajax get request without same-domain checks.)

However, since foo.js is on the same domain than the page you can fetch it with an ajax request. Example with jQuery:

$.get('foo.js', function(source_code) {
    alert('foo.js contains ' + source_code);
});

Answer 2

No, not directly for fundamental security reasons.

The fact that you've tagged this with Ajax implies that you're trying to use this as a way to retrieve data. If so, the closest similar approach is JSONP, in which the newly loaded script invokes a method to pass data back to the parent document.