p5.js flocking example is slow and laggy on all browsers

My goal is to make generative art and basic web games using p5.js and python flask as backend.

Though when I am trying out the demo flocking on all browsers, even without adding additional units, it's seemingly skipping framerate. And with adding more flocking units, they will consistently move in slow-motion. And it will use up my CPU at around 50-70%.

Is this expected with p5.js? Anyway to speed up so it can remain at certain framerate (i.e., 40 Fps)?