game.js

const {GRID_SIZE} = require ('./constants');

module.exports = {
    createGameState,gameLoop,
}
function createGameState(){
    return {
        player: {
            pos:{
                x:3,
                y:10,
            },
            vel:{
                x:1,
                y:0,
            },
            snake:[
                {x:1,y:10},
                {x:2,y:10},
                {x:3,y:10},
        ],
    },
        food:{
            x:7,
            y:7,
        },
        gridsize: GRID_SIZE,
        };
}

function gameLoop(state) {
  if (!state){
      return;
  }
  const playerOne = state.player;

  playerOne.pos.x +=playerOne.vel.x;
  playerOne.pos.y +=playerOne.vel.y;

  if (playerOne.pos.x<0 || playerOne.pos.x > GRID_SIZE || playerOne.pos.y<0 || playerOne.pos.y>GRID_SIZE){
      return 2;
  }

  if (state.food.x === playerOne.pos.x && state.food.y===playerOne.pos.y){
      playerOne.snake.push({ ...playerOne.pos});
      playerOne.pos.x +=playerOne.vel.x;
      playerOne.pos.y +=playerOne.vel.y;

      randomFood();

  }
  if (playerOne.vel.x || playerOne.vel.y){
      for(let cell of playerOne.snake){
          if (cell.x===playerOne.pos.x && cell.y ===playerOne.pos.y){
              return 2;
          }
      }
      playerOne.snake.push({...playerOne.pos});
      playerOne.snake.shift();
  }
  return false; //no winner 
}

function randomFood(state) {
    food ={
        x: Math.floor(Math.random() * GRID_SIZE),
        y: Math.floor(Math.random() * GRID_SIZE),
        
    }
    for (let cell of state.player.snake){
        if (cell.x===food.x && cell.y === food.y){
            return ransomFood(state);
        }
    }
    state.food = food;
}