index.js

class Grid {
  ...
  getFillStyle(state) {
    switch (state) {
      case 'on':
        return 'green';
      case 'off':
        return 'lightgrey';
      case 'food':
        return 'purple';
      default:
        return 'lightgrey';
    };
  }
}

class Game {
  constructor(grid, snake) {
    ...
    this.food = null;
  }

  async run() {

    setInterval(() => {
      if (this.food === null) {
        const x = Math.floor(Math.random() * (this.grid.width - 1 - 0)) + 0;
        const y = Math.floor(Math.random() * (this.grid.height - 1 - 0)) + 0;
        this.food = { x, y, isRendered: false };
      }
    }, 1000);

    while (true) {
      ...
      if (this.food) {
        if(!this.food.isRendered)
          grid.setPoint(this.food, 'food');
        this.food.isRendered = true;
      }
      ...
    }
  }