Capital letters are bigger, and therefore take up more space.

For minification, as someone else said. I originally wrote this for a JS1K competition some years ago, so it's not geared towards readability, but towards small code size.

I had a really, really ugly trick that saved me a couple of bytes which I removed before posting to HN. I figured out I was using canvas.getImageData() and canvas.putImageData(). So I did this: var tID = "tImageDatA"; canvas["ge"+tID](); canvas["pu"+tID"](); You can see that in the original source: http://gabrielgambetta.com/tiny_raytracer_full.js

Not my proudest hack :D

Because when it's run through the Google closure compiler it becomes

    E=Math,F=E.sqrt,G=E.max

That is before minifying. The variable name "math" was chosen for readibility in the non-minified version. The variable math can be renamed during the minifying process to a short identifier, in this case "E". Since the Math object is used quite a lot, it is worth the assignment to rename it.

Closure compiler will rename the math variable.