Usually developers are more interested in just getting the dang code to work, and as a result actual the testing and maintenance of JavaScript isn’t talked about too much, so I’m sure this will be new territory for many developers. And since it’s John Resig speaking, there was of course a bit about using TestSwarm, a testing distributed framework-agnostic automated testing tool (that’s a mouthful!).

Included in the talk are good things to note while testing, such as the fact unless you’re running Firefox or Chrome on Windows, all test times have a margin of error of up to 15ms (not to be confused with PPK’s observation of the delay between JavaScript computation and browser rendering).

(via YUIBlog)

function jQuery(str, con){
    if ( window == this )
        return new jQuery(str, con);
    // ...
}

new jQuery("#foo"); // this is now equivalent...
jQuery("#foo");     // ...to this!

Explanation: when jQuery(“#foo”) is typed, the function first determines if the context in which it’s being called is the global object (window).  If it is, it returns an instantiation of itself.  When it’s instantiated, the context in which it’s being called is inside its own function, and NOT within the global object (window), thus it bypasses our little instantiation trick and moves on to execute any remaining code in the function.

From John Resig’s Best Practices in Javascript Library Design