kontra/src/vector.js

Kontra HTML5 game development library

/**
 * A simple 2d vector object.
 *
 * ```js
 * import { Vector } from 'kontra';
 *
 * let vector = Vector(100, 200);
 * ```
 * @class Vector
 *
 * @param {Number} [x=0] - X coordinate of the vector.
 * @param {Number} [y=0] - Y coordinate of the vector.
 */
class Vector {
  constructor(x, y) {
    this._x = x || 0;
    this._y = y || 0;
  }

  /**
   * Return a new Vector whose value is the addition of the current Vector and the passed in Vector. If `dt` is provided, the result is multiplied by the value.
   * @memberof Vector
   * @function add
   *
   * @param {kontra.Vector} vector - Vector to add to the current Vector.
   * @param {Number} [dt=1] - Time since last update.
   *
   * @returns {kontra.Vector} A new kontra.Vector instance.
   */
  add(vec, dt) {
    return vectorFactory(
      this.x + (vec.x || 0) * (dt || 1),
      this.y + (vec.y || 0) * (dt || 1)
    );
  }

  /**
   * Clamp the Vector between two points, preventing `x` and `y` from going below or above the minimum and maximum values. Perfect for keeping a sprite from going outside the game boundaries.
   *
   * ```js
   * import { Vector } from 'kontra';
   *
   * let vector = Vector(100, 200);
   * vector.clamp(0, 0, 200, 300);
   *
   * vector.x += 200;
   * console.log(vector.x);  //=> 200
   *
   * vector.y -= 300;
   * console.log(vector.y);  //=> 0
   *
   * vector.add({x: -500, y: 500});
   * console.log(vector);    //=> {x: 0, y: 300}
   * ```
   * @memberof Vector
   * @function clamp
   *
   * @param {Number} xMin - Minimum x value.
   * @param {Number} yMin - Minimum y value.
   * @param {Number} xMax - Maximum x value.
   * @param {Number} yMax - Maximum y value.
   */
  clamp(xMin, yMin, xMax, yMax) {
    this._c = true;
    this._a = xMin;
    this._b = yMin;
    this._d = xMax;
    this._e = yMax;
  }

  /**
   * X coordinate of the vector.
   * @memberof Vector
   * @property {Number} x
   */
  get x() {
    return this._x;
  }

  /**
   * Y coordinate of the vector.
   * @memberof Vector
   * @property {Number} y
   */
  get y() {
    return this._y;
  }

  set x(value) {
    this._x = (this._c ? Math.min( Math.max(this._a, value), this._d ) : value);
  }

  set y(value) {
    this._y = (this._c ? Math.min( Math.max(this._b, value), this._e ) : value);
  }
}

export default function vectorFactory(x, y) {
  return new Vector(x, y);
}
vectorFactory.prototype = Vector.prototype;
vectorFactory.class = Vector;