Picking point from a disk with uniform distribution

const u = 100 * Math.random();
const theta = 2 * Math.PI * Math.random();

const x = Math.sqrt(u) * Math.cos(theta)
const y = Math.sqrt(u) * Math.sin(theta)

Useful Links

1. Point Picking and Distributing on the Disc and Sphere
2. Sector Of A Circle