Line Point Change

<!DOCTYPE html>
<html>
<head>
  <script src="https://cdn.rawgit.com/konvajs/konva/0.11.1/konva.min.js"></script>
  <meta charset="utf-8">
  <title>Konva Line Polygon Demo</title>
  <style>
    body {
      margin: 0;
      padding: 0;
      overflow: hidden;
      background-color: #F0F0F0;
    }
  </style>
</head>
<body>
  <div id="container"></div>
  <script src="script.js"></script>
</body>
</html>

function isInside(point, vertices) {
  // ray-casting algorithm based on
  // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html

  var i, j, xi, xj, yi, yj, intersect,
    x = point.x,
    y = point.y,
    inside = false;

  for (i = 0, j = vertices.length - 1; i < vertices.length; j = i, i += 1) {
    xi = vertices[i].x;
    yi = vertices[i].y;
    xj = vertices[j].x;
    yj = vertices[j].y;

    intersect = ((yi > y) !== (yj > y)) && (x < (xj - xi) * (y - yi) / (yj - yi) + xi);

    if (intersect) {
      inside = !inside;
    }
  }
  return inside;
}
// Code goes here

var width = window.innerWidth;
var height = window.innerHeight;

var stage = new Konva.Stage({
  container: 'container',
  width: width,
  height: height
});

var layer = new Konva.Layer();

var poly = new Konva.Line({
  points: [23, 20, 23, 160, 70, 93, 150, 109, 290, 139, 270, 93],
  fill: 'rgba(111,111,111,0.5)',
  stroke: 'black',
  strokeWidth: 5,
  closed: true,
  draggable: true
});
var blueCircle = new Konva.Circle({
  x: 50,
  y: 50,
  draggable: true,
  fill: 'blue',
  stroke: 'black',
  radius: 10
});
var redCircle = new Konva.Circle({
  x: 150,
  y: 150,
  draggable: true,
  fill: 'red',
  stroke: 'black',
  radius: 10
});

poly.on('dragmove', function(e) {

});

poly.on('dragend', function(e) {
  var vs = [],
    //getting line point but don't know why always get same point.
    points = poly.getPoints();
  for (var i = 0; i < points.length; i += 2) {
    vs.push({
      x: points[i],
      y: points[i + 1]
    });
  }
  console.log('Blue, isInside: ' + isInside(blueCircle.getPosition(), vs));
  console.log('Red, isInside: ' + isInside(redCircle.getPosition(), vs));
  //same points after drag
  console.log('Same points after drag ',points);
});
layer.add(blueCircle);
layer.add(redCircle);
// add the shape to the layer
layer.add(poly);

// add the layer to the stage
stage.add(layer);

/* Styles go here */