Javascr ipt实现的贪吃蛇游戏 功能：蛇吃食物有三种情况：走到的地方有食物；走到的地方没有食物；走到的地方是墙壁。吃到食物后，蛇的身体会变长；碰到墙壁后 Game Over，询问是否重新开始。 -Javascr ipt implementation of the Snake game features: snake eating food in three ways: go to where there is food　go where no food　place went to the wall. After eating the food, the snake' s body becomes longer　hit the wall after Game Over, asking whether to start over.