Comment by austincheney

The one example that comes to mind is file system search.

I am writing this application that displays the file system in the browser in a GUI much like Windows Explorer or OSX Finder. It performs file system search substantially faster than Windows Explorer. Windows Explorer is written in a lower level language with decades of usage and experience where my application is a one man hobby project written in JavaScript (TypeScript).

The reason why the hobby project is so substantially faster than a piece of core technology of the flagship product of Microsoft is that it does less.

First, you have to understand how recursive tree models work. You have a general idea of how to access nodes on the tree, but you have no idea what’s there until you are close enough to touch it. File system access performance is limited by both the hardware on which the file system resides and the logic on the particular file system type. Those constraints erode away some of the performance benefits of using a lower level language. What ever operations you wish to perform must be individually applied on each node because you have no idea what’s there until you are touching it.

Second, because the operations are individually applied on each node it’s important to limit what those operations actually are. My application is only searching against a string fragment, absence of the string fragment, or a regular expression match. Wildcards are not supported and other extended search syntax is not supported. If you have to parse a rule each time before applying it to a string identifier of a node those are additional operations performed at each and every node in the designated segment of the tree.

For those familiar with the DOM in the browser it also has the same problems because it’s also a tree model. This is why querySelectors are so incredibly slow compared to walking the DOM with the boring old static DOM methods.