old_contents: export default class Item extends Phaser.Sprite {
      constructor (game, x, y, key, frame) {
          super(game, x, y, key, frame);
  
          this.game.physics.enable(this, Phaser.Physics.ARCADE);
  
          this.spawnRate = 1; // value between 0 and 1, 1 means always 0 means practically never
      }
  }
  
new_contents: export default class Item extends Phaser.Sprite {
      constructor (game, x, y, key, frame) {
          super(game, x, y, key, frame);
  
          this.game.physics.enable(this, Phaser.Physics.ARCADE);
  
          this.spawnRate = 1; // value between 0 and 1, 1 means always 0 means practically never
      }
  
      update () {
          if (this.x < this.width) { // kill items when they are off the screen
              this.destroy();
          }
      }
  }
  
subject: destroy items that fly off the screen