Changes

The original Processing Language was is written in Java and the syntax is Java based. Sketches written in Processing can then be compiled into standalone applications or Java Applets. Processing.js interprets Processing sketches and creates JavaScript code that renders on a web page. When the original Processing Language, was first developed, Java was supposed to become the language of the web while JavaScript was a client-side scripting language for small tasks. As the web matured, JavaScript, however, became the language of the web, although many of the misconceptions about it still persist. /*(cite javascript JavaScript the good parts here*/ ) With recent developments in JavaScript technology, JavaScript is now fast enough to handle the demands of real-time interactive multimedia web applications such as games.

From it's inception, Processing.js was designed to be more than just a rewrite of the Java functions provided by Processing to JavaScript. John Resig wrote the original Processing.js parser to scan a Processing sketch for hints of Java code and translate that code to JavaScript. However, if the parser encountered JavaScript code, it would leave the code intact as JavaScript. This method allowed allows not only allows for the interpretation of existing Processing code but also the injection of JavaScript into Processing sketches. By allowing JavaScript to exist within a Processing Sketch intact, JavaScript code can exist inside a Processing sketch without any need to declare the language you are using. Old sketches written for Processing will work but new sketches written for Processing.js can easily make use of common web libraries such as JQuery or pull in resources from web services such as Twitter of , Google maps, or Flickr.

The original code for Processing.js used regular expressions to convert Java into JavaScript when it was encountered. It did this by scanning for hints of Java code within the entire sketch and then replaced the Java code with its JavaScript equivalent. Due to the difference in how Java and JavaScript accessed object properties from methods inside an object, the with statement was used as a simple solution to avoid having to prepend all function calls with "this." or "Processing.". However, the use of the with statement also meant that the JavaScript generated would fall off Trace /*(cite trace paper here... do we need to talk about trace in the back ground section???*/ ) making the code run slower than it needed to in some browsers. In later versions of Processing.js this method of scanning the entire sketch was replaced by the creation of an abstract syntax tree that broke up the up the sketch into smaller pieces. Each piece was then interpreted separately. This change made the interpretation of the sketch far cleaner.