index.js

class Snake {
  constructor(position) {
    this.parts = [position];
  }
  
  update() {
    let updates = [];
    updates.push({
      point: this.head,
      state: 'on'
    });
    return updates;
  }
  
  get head() {
    return Object.assign({}, this.parts[0]);
  }
}

...

const grid = new Grid(width, height, blockarea, margin, ctx);

const snake = new Snake({x:10, y:10});
const updates = snake.update();
updates.forEach(x => {
  grid.setPoint(x.point, x.state);
});

grid.render();