改个js编写的贪吃蛇

Question

想实现一个允许经过蛇身的贪吃蛇代码，在下面的代码上进行更改
#介绍，该代码思路，划出从左到右，从上到下400个20x20格子，通过不断画蛇头和判断涂黑蛇尾模拟移动.
#现在的问题在于蛇头经过蛇身时该如何更改，应该需要在下面注释的代码那里更改，emm，个人尝试了好多次总是出现bug.

    <canvas id="can" width="400" height="400" style="background-color: black;"></canvas>
    <script>
        var snake = [48, 47, 46, 45, 44, 43, 42, 41, 40],
            direction = 1,
            food = 49,
            n,
            nm = 0
        box = document.getElementById('can').getContext('2d');

        function randint(x, y) {
            return parseInt(Math.random() * (x - y + 1) + y);
        }
        function draw(seat, color) {
            box.fillStyle = color;
            box.fillRect(seat % 20 * 20 + 1, ~~(seat / 20) * 20 + 1, 18, 18);
        }
        document.onkeydown = function(evt) {
            direction = snake[1] - snake[0] == (n = [-1, -20, 1, 20][(evt || event).keyCode - 37] || direction) ? direction : n;
        };
        ! function() {
            snake.unshift(n = snake[0] + direction);
            if (n < 0 || n > 399 || direction == 1 && n % 20 == 0 || direction == -1 && n % 20 == 19) {
                nm -= 1
                return alert("GAME OVER!" + nm + "分");
            }
            draw(n, "lime");
            if (n == food) {
                while (snake.indexOf(food = randint(20, 380)) > 0);
                draw(food, "yellow");
                nm += 1
            } else {
               // var tem = snake[0];
               // if (snake.indexOf(tem) <= 1) {
               //     draw(snake.pop(), "black")
              //  }
            }
            setTimeout(arguments.callee, 88);
        }();
    </script>

Answer 1

已经解决，不是该判断思路，而是增加一个修补

for (i in snake){
     if (snake[i]==tem){
          draw(tem,"lime");
          break;}
}