homework.js

/* Homework */

var sqrt = Math.sqrt;
var pow = Math.pow;
var random = Math.random;

/* POINT */

var Point = function (x, y) {
  if (!(this instanceof Point)){
	return new Point(x, y);
  }
  this.x = x || 0;
  this.y = y || 0;
};

Point.prototype.translate = function(dx, dy) {
  this.x += dx;
  this.y += dy;

  return this;
};

var randomPoint = function () {
  var x1 = random() * 200 - 100;
  var y1 = random() * 200 - 100;
  
  return new Point(x1, y1);
};

var randomPoints = function (n) {
  var n = n || 1;
  var res = new Array(n);

  for (var i = 0; i < n ; i += 1) {
    res[i] = randomPoint();
  }

  return res;
};

var points = randomPoints(100);

var filterBisettrice = function (arrayPunti){

  return arrayPunti.filter(function(item, index, array){
    return (item.y-item.x > 0);
  });

};

Point.prototype.membership = function (eqFunction){
  var piano = eqFunction(this.x,this.y);
  return (piano > 0)? 1 : (piano <0)? -1: 0;
};

Point.prototype.getDistanceFromPoint = function(point) {
  return sqrt(pow(point.y - this.y, 2) + pow(point.x - this.x, 2));
};

Point.prototype.getDistanceFromLine = function (line){
  return ((Math.abs(line.a*this.x + line.b*this.y + line.c))/(sqrt(pow(line.a,2) + pow(line.b,2))));
};

Point.prototype.getDistance = function (x){
  if ( x instanceof Point) {
    return this.getDistanceFromPoint(x);
  }

  if ( x instanceof Line) {
    return this.getDistanceFromLine(x);
  }

  throw  new Error('x is not a Point neither a Line');
};
/* TRIANGLE */

var Triangle = function (p1, p2, p3) {
  
if(!(this instanceof Triangle)){
	return new Triangle(p1, p2, p3);
  }

  this.points = [p1, p2, p3];

  this.lengths = this.points.map(function(item, index, array){
      if(index === (array.length - 1) ){
        return item.getDistance(array[0]);
      }
      return item.getDistance(array[index+1])
  });
};

Triangle.prototype.getPerimeter = function() {
  var perimiter = 0;
  this.lengths.forEach(function(item){
	perimiter += item;
  });
  return perimiter;
};

Triangle.prototype.getArea = function() {
  var p = this.getPerimeter() / 2;
  var area = 1;
  this.lengths.forEach(function(item){
	area *= (p-item);
  });
  return sqrt(area*p);
};


Triangle.prototype.above = function (line){

  return this.points.every(function(item) { 
    return (item.getDistance(line) > 0);
  });

};

Triangle.prototype.below = function (line){

  return this.points.every(function(item,index,array){ 
	return (item.getDistance(line) < 0);
  });

};

Triangle.prototype.intersect = function (line){

  return (!this.above(line)&&!this.below(line));

};

/* LINE */
var Line = function (a, b, c){

  //Per forzare a lanciare cil costruttore con il new anche se l'utente non lo mette
  if(!(this instanceof Line)) {
    return new Line(a, b, c);
  }

  this.a = a;
  this.b = b;
  this.c = c;
};

/* Quad */

var Quad = function (p1, p2, p3, p4) {
  
if(!(this instanceof Quad)){
  return new Quad(p1, p2, p3, p4);
  }

  this.points = [p1, p2, p3, p4];

  this.lengths = this.points.map(function(item, index, array){
      if(index === (array.length - 1) ){
        return item.getDistance(array[0]);
      }
      return item.getDistance(array[index+1])
  });
};

Quad.prototype.getPerimeter = Triangle.prototype.getPerimeter;
Quad.prototype.getArea = Triangle.prototype.getArea;
Quad.prototype.above = Triangle.prototype.above;
Quad.prototype.below = Triangle.prototype.below;
Quad.prototype.intersect = Triangle.prototype.intersect;