Drawing an ASCII circle

circle.js

const drawASCIICircle = radius => {
  // x^2 + y^2 = radius^2 draws a circle

  const expectedValue = radius ** 2;

  // imagine a graph with the centre of a circle right on point (0, 0)
  for (let y = -radius; y <= radius; y++) {
    // y first, because we go across before we go down (inner loop runs more often)
    for (let x = -radius; x <= radius; x++) {
      const computedValue = x ** 2 + y ** 2;
      // use radius to get a roughly single-thickness circle - double or halve this for corresponding results
      if (Math.abs(computedValue - expectedValue) <= radius) {
        process.stdout.write("*");
      } else {
        process.stdout.write(" ");
      }
    }
    process.stdout.write("\n");
  }
};

drawASCIICircle(10); // draws circle of radius 10