The Deep exploration of the function overload of JavaScript implementation

javascript| function

<script>
function point2d (x, y)
{
this.x = x;
This.y = y;
Point2D.prototype.quadrant = function ()
{
if (x > 0 && y > 0) return "I";
else if (x < 0 && y > 0) return "II";
else if (x < 0 && y < 0) return "III";
else if (x > 0 && y < 0) return "IV";
else if (x = = 0) return "x-axis";
else if (y = = 0) return return "Y-axis";
else throw new Error ();
}
Point2D.prototype.toVector = function ()
{
return new vector2d (x, y);
}
Point2D.prototype.distance = function ()//Distance
{
if (arguments.length = = 1 && arguments[0] instanceof point2d)
{
Return this._point_distance.apply (this, arguments);
}
else if (arguments.length = = 1 && arguments[0] instanceof vector2d)
{
Return this._vector_distance.apply (this, arguments);
}
Else
{
throw new Error ("Argument error!");
}
}
point2d.prototype._point_distance = function (p)//find the distance between two points (function overload)
{
Return (new Vector2d (P,this)). Length ();
}
Point2d.prototype._vector_distance = function (v)//distance from point to vector (function overload)
{
var v1 = new Vector2d (this, v.start);
var v2 = new Vector2d (this, v.end);

var area = Math.Abs (V1.cross (v2)); Parallelogram area = V1 X v2 = |v1v2|sin (V1,V2)

return Area/v.length (); The parallelogram area divided by the bottom length is the distance from point to vector
}
}
function vector2d ()
{
if (arguments.length = = 2 && arguments[0] instanceof point2d && arguments[1] instanceof point2d)
{
_point_point_vector2d.apply (this, arguments);
}
else if (arguments.length = = 2 &&!isnan (arguments[0)) &&!isnan (arguments[1))
{
_double_double_vector2d.apply (this, arguments);
}
else if (arguments.length = = 4 &&!isnan (arguments[0)) &&!isnan (arguments[1))
&&!isnan (arguments[2]) &&!isnan (arguments[3))
{
_double_double_double_double_vector2d.apply (this, arguments);
}
Else
{
throw new Error ("Argument error!");
}
}
function _point_point_vector2d (p1, p2)
{
This.start = p1;
This.end = p2;
Vector2D.prototype.length = function ()//Find the length of a vector
{
Return Math.sqrt (this.pond_x () * this.pond_x () + this.pond_y () * this.pond_y ());
}
Vector2D.prototype.pond_x = function ()//x direction component
{
return this.start.x-this.end.x;
}
Vector2D.prototype.pond_y = function ()
{
return this.start.y-this.end.y;
}
Vector2D.prototype.cross = function (v)//quadrature of vector P1 X P2 = x1y2-x2y1
{
return this.pond_x () * v.pond_y ()-v.pond_x () * this.pond_y ();
}
}
function _double_double_vector2d (x,y)//overloaded constructors vector2d
{
This.pointpairs = new Array ();
This.pointpairs[0] = new point2d (0, 0);
THIS.POINTPAIRS[1] = new point2d (x, y);

_point_point_vector2d.apply (this, this.pointpairs);
}
function _double_double_double_double_vector2d (x1, y1, x2, y2)//overloaded constructors vector2d
{
This.pointpairs = new Array ();
This.pointpairs[0] = new POINT2D (x1, y1);
THIS.POINTPAIRS[1] = new point2d (x2, y2);

_point_point_vector2d.apply (this, this.pointpairs);
}
var p1 = new point2d (0,0);
var P2 = new point2d (10,10);
var v1 = new Vector2d (P1,P2); The vector V1 is constructed by means of a two-point (P1,P2)
Alert ("Vector v1 length:" +v1.length ());
var v2 = new vector2d (0,0,5,5); A vector V2 is constructed by means of four coordinates (X1,Y1,X2,Y2)
Alert ("Vector v2 Length:" +v2.length ());
var v3 = new vector2d (0,10); Constructs a vector V3 by specifying the end point
Alert ("Vector v3 length:" +v3.length ());
Alert ("Vector v1 with v2": +v1.cross (v2)); Find V1 X V2 (because parallel, so the result is 0)

var p3 = new point2d (10,0);
Alert ("Point P1 distance from P3:" +p1.distance (p3));
Alert ("The distance from the point P3 to the vector v1:" +p3.distance (v1));
</script>