Vector2D

A 2D vector class for positions, velocities, forces, and directions. Every moving object in every DN game has a Vector2D pos and usually a Vector2D vel.

Include

<script src="/js/dn/mathUtils.js"></script>

Vector2D is defined in mathUtils.js alongside standalone helpers like clamp, lerp, xFromDistAngle, and yFromDistAngle.

Constructor

const v = new Vector2D(x, y);  // defaults: x=0, y=0
const zero = new Vector2D();   // (0, 0)

Properties

Methods

All methods that return a new vector do not modify this — they return a new Vector2D. Methods that modify in-place (like normalize(), setMag()) are noted.

v.add(other)         // returns new Vector2D(v.x + other.x, v.y + other.y)
v.subtract(other)    // returns new Vector2D(v.x - other.x, v.y - other.y)
v.scale(s)           // returns new Vector2D(v.x * s, v.y * s)
v.multiply(other)    // component-wise multiply, returns new Vector2D
v.divide(other)      // component-wise divide, returns new Vector2D
v.clone()            // returns a copy of this vector

v.getMag()           // returns √(x² + y²)
v.normalize()        // modifies in-place — sets length to 1
v.getNormalized()    // returns a normalized copy, does not modify this
v.setMag(m)          // modifies in-place — normalizes then scales to m
v.dot(other)         // returns dot product (scalar)

v.distanceTo(other)  // returns distance between two points
v.toString()         // "Vector2D(x.xxx, y.xxx)"

Common Patterns

Moving an object at constant speed

const pos = new Vector2D(100, 100);
const vel = new Vector2D(200, -150);  // pixels per second

function update(dt) {
  pos.x += vel.x * dt;
  pos.y += vel.y * dt;
}

Pointing one object toward another

const diff = target.pos.subtract(entity.pos);  // direction vector
diff.setMag(entity.speed);                      // scale to speed
entity.vel = diff;                              // point toward target

Gravity / attraction force (used in LoopShoots)

const diff = new Vector2D(
  attractor.pos.x - ball.pos.x,
  attractor.pos.y - ball.pos.y
);
diff.setMag(gravityStrength);     // normalize + set pull force
ball.vel.x += diff.x;
ball.vel.y += diff.y;
ball.vel.setMag(ball.speed);      // clamp to max speed

Standalone Math Helpers (same file)

// Polar → cartesian (used in orbit/circle animations)
xFromDistAngle(distance, angle, isDegrees = false)
yFromDistAngle(distance, angle, isDegrees = false)

// Clamp a value between min and max
clamp(value, min, max)

// Linear interpolation
lerp(a, b, t)  // t = 0..1

Source

public/js/dn/mathUtils.js