Is there a way to “hot swap” JavaScript code within the browser?

Question

Is there any tool that enables you to \"hot swap\" JavaScript contents while executing a webpage?

I am looking for something similar to what HotSpot does for Java,

Answer 1

im sure not too many people here know what you mean by hot swap but as virtuosiMedia said mootools allows that, if you dont trust mootools that much then there's a same plugin for jquery and still if you dont want frameworks you could always add those scripts via dom

but i'm sure you are not allowed to alter the head level scripts you've already defined as any scripts dynamically added through DOM is only body level