lineSegmentIntersect.js

(function intersect() {
  const LOOPS = 2.5 * 10 ** 8;
  let count = 0;
  const { random: r, sqrt: s } = Math;
  for (let i = 0; i < LOOPS; i++) {
    let x = r();
    let y = r();
    const a = { x, y };
    x = r();
    y = r();
    const b = { x, y };
    const line1 = {
      slope: a.y / a.x,
      cut: 0
    };
    const line2 = {
      slope: (1 - b.y) / (1 - b.x)
    };
    line2.cut = b.y - line2.slope * b.x;
    const X = line2.cut / (line1.slope - line2.slope);
    const Y = (line1.slope * line2.cut) / (line1.slope - line2.slope);
    const da = s(a.x ** 2 + a.y ** 2);
    const db = s((b.x - 1) ** 2 + (b.y - 1) ** 2);
    const dXY0 = s(X ** 2 + Y ** 2);
    const dXY1 = s((X - 1) ** 2 + (Y - 1) ** 2);
    if (Y >= 0 && Y <= 1 && X >= 0 && X <= 1 && dXY0 <= da && dXY1 <= db)
      count++;
  }
  console.log(`Intersect within the square: ${(count * 100) / LOOPS}%`);
})();