Javascript TypeError:此网格[x]未定义
我正在尝试从JavaScript和画布中的一个脚本构建一个蛇游戏。此时,我正在接收一个错误(TypeError:y未定义),在这行:Javascript TypeError:此网格[x]未定义,javascript,canvas,Javascript,Canvas,我正在尝试从JavaScript和画布中的一个脚本构建一个蛇游戏。此时,我正在接收一个错误(TypeError:y未定义),在这行: return this._grid[x][y]; 它是var网格对象的一部分。如果有人能给我指出正确的方向,我会非常感激,这样我就可以完成比赛了!!! 谢谢 <script> //Constants var COLS = 26, ROWS = 26; // IDs var EMPTY=0, SNAKE = 1, FRUIT = 2; // Direc
return this._grid[x][y];
它是var网格对象的一部分。如果有人能给我指出正确的方向,我会非常感激,这样我就可以完成比赛了!!!
谢谢
<script>
//Constants
var COLS = 26, ROWS = 26;
// IDs
var EMPTY=0, SNAKE = 1, FRUIT = 2;
// Directions
var LEFT = 0, UP = 1, RIGHT = 2, DOWN = 3;
// KeyCodes
var KEY_LEFT=37, KEY_UP=38, KEY_RIGHT=39, KEY_DOWN=40;
var grid = {
width: null,
height: null,
_grid: null,
init: function(d,c,r){
this.width = c;
this.height = r;
this._grid = [];
for(var x=0; x<c; x++){
this._grid.push([]);
for(var y=0; y < r; y++){
this._grid[x].push(d);
}
}
},
set: function(val,x,y){
this._grid[x][y] = val;
},
get: function(x,y){
return this._grid[x][y];
}
}
var snake = {
direction: null,
last: null,
_queue: null,
init: function(d,x,y){
this.direction = d;
this._queue = [];
this.insert(x,y);
},
insert: function(x,y){
this._queue.unshift({x:x, y:y});
this.last = this._queue[0];
},
remove: function(){
return this._queue.pop();
}
}
function setFood() {
var empty = [];
for (var x = 0; x < grid.width; x++) {
for (var y = 0; y < grid.height; y++) {
if (grid.get(x, y) === EMPTY) {
empty.push({x:x, y:y});
}
}
}
var randpos = empty[Math.floor(Math.random()*empty.length)];
grid.set(FRUIT, randpos.x, randpos.y);
}
//Game objects
var canvas, ctx, keystate, frames, score;
function main() {
canvas = document.createElement("canvas");
canvas.width = COLS*20;
canvas.height = ROWS*20;
ctx = canvas.getContext("2d");
document.body.appendChild(canvas);
ctx.font = "12px Helvetica"
frames = 0;
keystate = {};
document.addEventListener("keydown", function(evt) {
keystate[evt.keyCode] = true;
});
document.addEventListener("keyup", function(evt) {
delete keystate[evt.keyCode];
});
init();
loop();
}
function init(){
grid.init(EMPTY, COLS, ROWS);
var sp = {x:Math.floor(COLS/2), y:ROWS-1};
snake.init(UP, sp.x, sp.y);
grid.set(SNAKE, sp.x, sp.y);
setFood();
}
function loop(){
update();
draw();
window.requestAnimationFrame(loop, canvas);
}
function update() {
frames++;
if (keystate[KEY_LEFT] && snake.direction !== RIGHT)
snake.direction = LEFT;
if (keystate[KEY_UP] && snake.direction !== DOWN)
snake.direction = UP;
if (keystate[KEY_RIGHT] && snake.direction !== LEFT)
snake.direction = RIGHT;
if (keystate[KEY_DOWN] && snake.direction !== UP)
snake.direction = DOWN;
if (frames%5 === 0) {
var nx = snake.last.x;
var ny = snake.last.y;
switch (snake.direction) {
case LEFT:
nx--;
break;
case UP:
ny--;
break;
case RIGHT:
nx++;
break;
case DOWN:
ny++;
break;
}
if (grid.get(nx, ny) === FRUIT) {
var tail = {x:nx, y:ny};
score++;
setFood();
} else {
var tail = snake.remove();
grid.set(EMPTY, tail.x, tail.y);
tail.x = nx;
tail.y = ny;
}
grid.set(SNAKE, tail.x, tail.y);
snake.insert(tail.x, tail.y);
}
if (0 > nx || nx > grid.width-1 ||
0 > ny || ny > grid.height-1
|| grid.get(nx, ny) === SNAKE
) {
return init();
}
}
function draw() {
var tw = canvas.width/grid.width;
var th = canvas.height/grid.height;
for (var x = 0; x < grid.width; x++) {
for (var y = 0; y < grid.height; y++) {
switch (grid.get(x, y)) {
case EMPTY:
ctx.fillStyle = "#fff";
break;
case SNAKE:
ctx.fillStyle = "#0ff";
break;
case FRUIT:
ctx.fillStyle = "#f00";
break;
}
ctx.fillRect(x*tw, y*th, tw, th);
}
}
ctx.fillStyle = "#000";
ctx.fillText("SCORE: " + score, 10, canvas.height-10);
};
main();
</script>
//常数
var COLS=26,ROWS=26;
//身份证
空变量=0,蛇=1,果=2;
//方向
var LEFT=0,UP=1,RIGHT=2,DOWN=3;
//键码
var KEY_LEFT=37,KEY_UP=38,KEY_RIGHT=39,KEY_DOWN=40;
变量网格={
宽度:空,
高度:空,
_网格:空,
init:函数(d,c,r){
这个宽度=c;
这个高度=r;
这个。_网格=[];
对于(var x=0;x nx | | nx>grid.width-1||
0>ny | | ny>grid.height-1
||grid.get(nx,ny)==SNAKE
) {
返回init();
}
}
函数绘图(){
var tw=canvas.width/grid.width;
var th=canvas.height/grid.height;
对于(var x=0;x
如果传递的数据不能保证在正确的范围内,则需要检查或捕获超出范围的值
如果您认为数据不需要检查,则需要找到索引未定义数组项的坏值x的来源
对于调试,可以在getter中添加一个断点并使用调试器找出x的哪个值不正确并抛出错误,或者将调试器设置为“出错时中断”,并检查给出错误引用的x的值
将get函数更改为
get: function(x,y){
try{
return this._grid[x][y];
} catch(e){
console.error("access to _grid["+x+ "][" + y +"] failed");
throw e;
}
}
因此,当抛出错误时,您可以看到x值是多少
找到原因并解决问题后,您可以删除try-catch您正在调用此函数
grid.get(x,y)
几次。在哪个调用之后会出现此错误?@krzywiecki我认为它是从条件中调用的-if(…| grid.get(nx,ny)==SNAKE)
在更新功能的底部。