Canvas + JQuery实现贪吃蛇demo

注：IE 8 或更早的浏览器不支持 元素。

涉及核心函数:

• fillRect:
  绘制“已填色”的矩形。默认的填充颜色是黑色。

var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.fillRect(20,20,150,100);

• clearRect
  清空给定矩形内的指定像素。

var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.fillStyle="red";
ctx.fillRect(0,0,300,150);
ctx.clearRect(20,20,100,50);

代码:

• HTML:

• JS:
  注释已给出,不再赘述

$(function() {
      // init global variable
      var speed = 100;
      var x = 0;
      var y = 0;
      var direction = 'r'; // l = left, r = right, u = up, d = down
      var path = [];
      var foodLocation = {};

      var canvasInit = function() {
        canvasWidth = 600;
        canvasHeight = 600;
        $('#snake').attr('width', canvasWidth);
        $('#snake').attr('height', canvasHeight);
        $('#snake').css('border', '1px solid #c3c3c3');
        $('#snake').css('background-color', '#e8e4e4');
      }

      var snakeInit = function() {
        snakeLength = 10; // this is the length of blocks-unit
        snakeSize = 10;
        o_snake = document.getElementById("snake").getContext("2d");
        o_snake.strokeStyle = "#fff";
        o_snake.fillStyle = "#000";
        foodInit();
      }

      var foodInit = function() {
        // make the location right with snake-size-blocks
        foodLocation.x = parseInt(Math.random() * (canvasWidth/snakeSize - snakeSize)) * snakeSize;
        foodLocation.y = parseInt(Math.random() * (canvasHeight/snakeSize - snakeSize)) * snakeSize;
        o_snake.fillRect(foodLocation.x, foodLocation.y, snakeSize, snakeSize);
      }

      var snakeMove = function(direction, path, o_snake, snakeSize) {
          foodCheck();
          switch (direction) {
            case 'l' :
              x = x - snakeSize;
              break;
            case 'r' :
              x = x + snakeSize;
              break;
            case 'u' :
              y = y - snakeSize;
              break;
            case 'd' :
              y = y + snakeSize;
              break;
          }
          // live check must be here, for x&y have been reseted
          liveCheck();
          // update snake block
          path.push({
            'x': x,
            'y': y
          });
          // clear latest snake block
          if (path.length > snakeLength) {
            var r_path = path.shift();
            o_snake.clearRect(r_path['x'], r_path['y'], snakeSize, snakeSize);
          }
          // draw newest snake block
          o_snake.fillRect(x, y, snakeSize, snakeSize);
      }

      var snakeGrow = function() {
        snakeLength ++;
        foodInit();
      }

      var liveCheck = function () {
        if (x > canvasWidth || y > canvasHeight || x < 0 || y < 0) {
          gameOver();
        }
        else if (typeof path[0] !== 'undefined') {
          for (var i = 0; i < path.length; i++) {
            console.log(parseInt(path[i].x));
            console.log(parseInt(foodLocation.x));
            if (parseInt(path[i].x) == x && parseInt(path[i].y) == y) {
              gameOver();
            }
          }
        }
      }

      var foodCheck = function() {
        for (var i = 0; i < path.length; i++) {
          if (parseInt(path[i].x) == parseInt(foodLocation.x) && parseInt(path[i].y) == parseInt(foodLocation.y)) {
            snakeGrow();
          }
        }
      }

      // we can do more interesting interaction here
      var gameOver = function() {
        alert('YOU DIED!');
        window.location.reload();
        return false;
      }

      // keyborad map
      $(document).keydown(function(e) {
        var keycode = e.keyCode;
        switch (keycode) {
          case 37 :
            direction = 'l';
            break;
          case 38 :
            direction = 'u';
            break;
          case 39 :
            direction = 'r';
            break;
          case 40 :
            direction = 'd';
            break;
        }
        snakeMove(direction, path, o_snake, snakeSize);
      });

      // events
      canvasInit();
      snakeInit();
      interval = window.setInterval(function() {snakeMove(direction, path, o_snake, snakeSize);}, speed);
    });