2D Point to Line Segment distance function

point-to-line-2d.js

// Taken From:
// https://stackoverflow.com/questions/849211/shortest-distance-between-a-point-and-a-line-segment

function sqr (x) {
  return x * x;
}

function dist2 (v, w) {
  return sqr(v[0] - w[0]) + sqr(v[1] - w[1]);
}

// p - point
// v - start point of segment
// w - end point of segment
function distToSegmentSquared (p, v, w) {
  var l2 = dist2(v, w);
  if (l2 === 0) return dist2(p, v);
  var t = ((p[0] - v[0]) * (w[0] - v[0]) + (p[1] - v[1]) * (w[1] - v[1])) / l2;
  t = Math.max(0, Math.min(1, t));
  return dist2(p, [ v[0] + t * (w[0] - v[0]), v[1] + t * (w[1] - v[1]) ]);
}

// p - point
// v - start point of segment
// w - end point of segment
function distToSegment (p, v, w) {
  return Math.sqrt(distToSegmentSquared(p, v, w));
}

module.exports = distToSegment;
module.exports.squared = distToSegmentSquared;

Handy snippet thanks!
Here's the same thing modified to reuse partial results and accept data structures instead of lists...

Handy modification thanks!
Here's the same thing, compressed:

function distToSegment(p,ln){var n=ln.ex-ln.sx,r=ln.ey-ln.sy,x=n*n+r*r;if(0==x)return this.pd(p,ln.sx,ln.sy);var y=((p.x-ln.sx)*n+(p.y-ln.sy)*r)/x;return y=Math.max(0,Math.min(1,y)),this.pd(p,ln.sx+y*n,ln.sy+y*r)}function pd(p,x,y){return Math.hypot(x-p.x,y-p.y)}

It's still used like ret=distToSegment({x:5,y:8},{sx:1,sy:1,ex:9,ey:7});