Have you encountered a case where you are suspicious about the
performance issue in some part of the application and your
concern was dismissed? Imagine a typical comment like:  Don’t
worry. That function runs really fast.  While in many cases this
is a valid assertion, in other cases being fast is not enough.
Future web apps won’t be judged by how the individual pieces are
evaluated, rather by the way they run together in an orchestra.
A simple function like this:  Array.prototype.swap = function
(i, j) {     var k = this[i]; this[i] = this[j]; this[j] = k;
is rather innocent. There is not much you can do to optimize it.
Yet, when it is being invoked from an implementation of a very
inefficient sorting algorithm, the overall outcome would be
disastrous.  Page optimization  So far, typical discussions and
best practices on web page optimizations (WPO) are geared
towards two things: transport and interface responsiveness
optimizations. The former is about leveraging the available
bandwidth to its potential,