Approximate Pi from Random Points

You are given an array pts of points in the unit square. Each point is represented as an array of two numbers [x, y], where 0 <= x <= 1 and 0 <= y <= 1.

A point lies inside the quarter circle of radius 1 if x*x + y*y <= 1.

Write a function approx(pts) that returns an approximation of pi using the fraction of points that fall inside the quarter circle.

Assume:

• pts is never null
• pts contains at least one point
• every point has exactly two numeric coordinates

Example function signature:

function approx(pts) {
 return 0;
}