This detailed tutorial shows how to implement pure functions in JavaScript that are deterministic and referentially transparent, and create no side effects.

If you write JavaScript, you have probably used higher-order functions and not even noticed. If you have ever replaced a for loop with an array method, you’ve used higher-order functions.

IDG For starters, let’s create a function that draws a watercolor spot with a given position, radius, and hue. P5.js gives us a function to draw an ellipse that we already used last week.