因为你可能把你的素描不单单当作绘图的画布，故size()方法已经被createcanvas()方法取代，以此说明还可以创建其他元素。P5.js通过将画布从一个单一的桌面应用扩展到浏览器的方式，开启了Processing的强大能力。
http://www.sitepoint.com/processing-js-vs-p5-js-whats-difference/?utm_source=tuicool
1-Processing is an environment/programming language that is meant to make visual, interactive applications extremely easy to write. It can be used for everything from teaching children how to code to visualizing scientific data.
2-p5 is made to make coding accessible for artists, designers, educators, and beginners, and reinterprets this for today’s web
P5 is a direct JS port of the Processing language. Processing.js is a converter which interprets pure Processing code into JS on the fly. The latter requires you to learn Processing, but not JS, and vice versa.
P5js is a young and ambitious project that aims to bring visual programming to the masses in a manner more approachable than Processing was until now. While it is currently being forced to be dumbed down somewhat feature-wise, the team is hard at work porting the rest of the Processing language to this JS counterpart.
The advantages of using P5 over Processing.js are:
Writing JS code you’re probably already familiar with
Officially supported by the Processing Foundation
HTML DOM manipulation with the DOM library addon – adding common HTML elements to your P5 sketches and more
Lighter on the resources when not drawing
The advantage of using Processing.js:
You learn Processing and can use it in environments where it’s faster and more portable to non-web environments
Seems to have a steadier frame rate and performs better in both demos we tried
