A toString()’able point that allows addition

point.js

function Point(x, y) {
  if (arguments.length === 1 && typeof x === 'string') {
    return x.slice(1, -1)
      .split('}{')
      .map(function(tuple) {
        return tuple.split(',', 2).map(parseFloat)
      })
      .reduce(function(point, coords) {
        point.x += coords[0];
        point.y += coords[1];
        return point;
      }, new Point());
  }

  this.x = x || 0;
  this.y = y || 0;
}

Point.prototype.toString = function() {
  return '{' + [this.x, this.y] + '}';
}