Order points geometrically to build a line

pointsToLine.js

// Build a line from unsorted points,
// in a way that the length of the line is minimal.
var pointsToLine = (function() {
  // distance between two points
  function dist(p1, p2) {
    return Math.sqrt(Math.pow(p1[0] - p2[0], 2) + Math.pow(p1[1] - p2[1], 2));
  }

  // find insertion index
  function findIdx(line, point) {
      var idx = 0,
          i, dx, min;

      if (line.length === 0) {
        return 0;
      }

      // check alignment
      if (line.length === 1) {
        if (dist(origin, point) > dist(origin, line[0])) {
          return 1;
        } else {
          return 0;
        }
      }

      for (i = 0; i < line.length; i++) {
        dx = dist(point, line[i]);

        if (!min || dx <= min) {
          min = dx;
          idx = i;
        }
      }

      // check before
      if (idx > 0 && dist(line[idx - 1], line[idx]) < dist(line[idx - 1], point)) {
        idx++;
      } else {
        // check after
        if (idx < (line.length - 1) && dist(line[idx + 1], line[idx]) > dist(line[idx + 1], point)) {
          idx++;
        }
      }

      return idx;

  }

  // insert points into line
  return function(points, line) {
    line || (line = []);

    points.forEach(function(point) {
      line.splice(findIdx(line, point), 0, point);
    });

    return line;
  };
}();