Sprite.js

/**
 * The Sprite class represents a simple animated character for a game
 * @name Sprite
 * @constructor Sprite
 */

class Sprite {
  constructor(options = {}){

    /**
     * The x position of the sprite in pixels
     * @type {Number}
     * @memberOf Sprite#
     * @default
     */
    this.x = 0.0;

    /**
     * The y position of the sprite in pixels
     * @type {Number}
     * @memberOf Sprite#
     * @default
     */
    this.y = 0.0;

    /**
     * The x component of the velocity in pixels per second
     * @type {Number}
     * @memberOf Sprite#
     * @default
     */
    this.dx = 0.0;

    /**
     * The y component of the velocity in pixels per second
     * @type {Number}
     * @memberOf Sprite#
     * @default
     */
    this.dy = 0.0;

    /**
     * The max speed a sprite can move in either direction
     * @type {Number}
     * @memberOf Sprite#
     * @default
     */
    this.maxSpeed = 0.0;

    /**
     * The name of this Sprite
     * @type {String}
     * @memberOf Sprite#
     * @default
     */
    this.name = null;

    /**
     * The radius of this sprite in pixels for simple collision detection
     * @type {Number}
     * @memberOf Sprite#
     * @default
     */
    this.collisionRadius = 40;

    Object.assign(this, options);
  }

  /**
   * Updates this Sprite's Animation and its position based on the velocity.
   * @function
   * @memberOf Sprite#
   * @param {Number} elapsedTime The elapsed time in milliseconds since the previous update
   */
  update(elapsedTime){
    this.x += this.dx * elapsedTime;
    this.y += this.dy * elapsedTime;
    this.anim.update(elapsedTime);
  }

  /**
   * Returns the maxSpeed up to the speed limit
   * @function
   * @memberOf Sprite#
   * @param {Number} v Speed limit
   * @return {Number} maxSpeed up to speed limit
   */
  limitSpeed(v){
    if(this.maxSpeed){
      if(Math.abs(v) > this.maxSpeed){
        if(v > 0){
          return this.maxSpeed;
        }else if(v < 0){
          return this.maxSpeed;
        }else{
          return  0;
        }
      }else{
        return v;
      }
    }else{
      return v;
    }
  }

  /**
   * Gets this Sprite's current animation frame.
   * @function
   * @memberOf Sprite#
   * @return {AnimationFrame} The current frame of the Animation
   */
  getCurrentFrame(){
    if(this.anim){
      return this.anim.getCurrentFrame();
    }
  }

  /**
   * Draws the sprite
   * @function
   * @memberOf Sprite#
   * @param {Context} context The HTML5 drawing context
   */
  draw(context){
    if(this.anim){
      this.anim.draw(context, this.x, this.y);
    }
  }

  /**
   * Clones the instance of Sprite it is called upon
   * @function
   * @memberOf Sprite#
   * @return {Sprite} A clone of the Sprite
   */
  clone() {
    return new Sprite({
      anim: this.anim.clone()
    });
  }
}

module.exports = Sprite;