In order for Processing.js to closely match the functionality of the native Processing language some custom flags had to be created to make the library behave like the native language. Pjs directives are a set of commands that are embedded in a multiline comment at the top of the sketch to control a few aspects of how the sketch will work. Placing the directives in a multiline comment allows for backwards compatibility of sketches with native Processing so that sketches written in Processing.js can be run on the native Processing JAVA platform. There are currently three Processing.js directives. These directives add the ability to preload images before the sketch begins to run, and to toggle transparent backgrounds and anti-aliasing of lines.