Low-level languages, like C, have low-level memory management primitives like malloc() and free(). On the other hand, JavaScript values are allocated when things (objects, strings, etc.) are created and "automatically" free'd when they are not used anymore. The latter process is called garbage collection. This "automatically" is a source of confusion and gives JavaScript (and high-level languages) developers the impression they can decide not to care about memory management. This is a mistake.

This tutorial explains how to use the Heap Profiler for uncovering memory leaks in your applications.

For traditional pages where the user is encouraged to navigate from page to page, memory leaks should almost never be a problem. However, for any page that encourages interaction, memory management must be considered. Most realize that ultimately if too much memory is consumed the page will be killed, forcing the user to reload it. However, even before all memory is exhausted performance problems arise:

I remember it all, but there’s just one thing: I remember nothing about the book’s actual contents.