@rnacanvas/points.oopified

Installation

With npm:

npm install @rnacanvas/points.oopified

Usage

All exports of this package can be accessed as named imports.

// an example import
import { Point } from '@rnacanvas/points.oopified';

Point

The Point class represents a 2D point.

var p = new Point(28.1, -55.4);

p.x; // 28.1
p.y; // -55.4

// can be modified
p.x = 101.2;
p.y = 38.1;

// is iterable
[...p]; // [101.2, 38.1]

static matching()

Creates and returns a new Point instance matching a point-like object (e.g., an object with x and y properties).

var p = Point.matching({ x: 901.7, y: -11 });

p.x; // 901.7
p.y; // -11

displacementTo()

Returns a new Vector instance that is the vector going from the point to the specified point.

See @rnacanvas/vectors.oopified package for documentation on the Vector class.

var p = new Point(0, 0);
var d = p.displacementTo({ x: 1, y: Math.sqrt(3) });

d.x; // 1
d.y; // Math.sqrt(3)

d.magnitude; // 2
d.direction; // Math.PI / 3

displacementFrom()

Returns a new Vector instance that is the vector going from the specified point to the point that this method was called on.

See @rnacanvas/vectors.oopified package for documentation on the Vector class.

var p = new Point(0, 0);
var d = p.displacementFrom({ x: 1, y: Math.sqrt(3) });

d.x; // -1
d.y; // -Math.sqrt(3)

d.magnitude; // 2
d.direction; // -2 * Math.PI / 3

distanceTo()

Returns the distance from the point to the specified point.

var p = new Point(10, 10);

p.distanceTo({ x: 13, y: 14 }); // 5

distanceFrom()

An alias for the distanceTo() method.

var p = new Point(80, 70);

p.distanceFrom({ x: 75, y: 82 }); // 13

directionTo()

Returns the angle (in radians) that is the direction from the point to the specified point in the standard Cartesian coordinate system.

var p = new Point(0, 0);

p.directionTo({ x: 1, y: 0 }); // 0
p.directionTo({ x: 0, y: 1 }); // Math.PI / 2
p.directionTo({ x: -1, y: -1 }); // -3 * Math.PI / 4

directionFrom()

Returns the angle (in radians) that is the direction from the specified point to the point that this was method was called on in the standard Cartesian coordinate system.

var p = new Point(0, 0);

p.directionFrom({ x: 1, y: 0 }); // Math.PI
p.directionFrom({ x: 0, y: 1 }); // -Math.PI / 2
p.directionFrom({ x: -1, y: -1 }); // Math.PI / 4

RelativePoint

The RelativePoint class represents a point that is expressed relative to a reference point.

var refP; // reference point
var relP = new RelativePoint(refP);

refP.x = 57;
refP.y = -81;

// moves with the reference point
relP.x; // 57
relP.y; // -81

relP.x += 12;
relP.y -= 15;

refP.x = 102;
refP.y = 3;

relP.x; // 102 + 12
relP.y; // 3 - 15

The reference point must fulfill the TrackablePoint interface below.

interface TrackablePoint {
  readonly x: number;
  readonly y: number;

  // the listener is to be called whenever the point moves
  // (i.e., whenever its X or Y coordinates change)
  addEventListener(name: 'move', listener: () => void): void;
}

Listening for move events

Listeners can be attached that will be called whenever a relative point moves (i.e., whenever the reference point moves or its displacement from the reference point changes).

var refP; // reference point
var relP = new RelativePoint(refP);

var listener = () => {};
relP.addEventListener('move', listener);

refP.x += 1000;
listener; // called once

relP.x -= 12;
listener; // called a second time

relP.removeEventListener('move', listener);

relP.x += 20;
listener; // not called a third time