javascript:未定义获取对象
javascript: Getting object is not defined
当尝试引用在不同函数中创建的对象时，出现"对象未定义"错误。这听起来像是一个范围问题，除了这以前在不同的程序中工作过。
我得到的错误是"未捕获的参考错误：人未定义"。
下面列出了我的部分代码：请查看在buildMap（）函数中创建man对象的位置，以及我尝试在playGame（）函数中引用它的位置。
var canvas = document.querySelector("canvas");
var drawingSurface = canvas.getContext("2d");
var man;
// Map code
var EMPTY = 0;
var TREE_BOTTOM = 1;
var TREE_TOP = 2;
var SKY = 3;
var CLOUD = 4;
var CLOUD_LEFT = 5;
var CLOUD_RIGHT = 6;
var PLATFORM = 7;
var EGG = 8;
var CAVE = 9;
var MEAT = 10;
var MAN = 11;
var DINO = 12;
var GUARD = 13;
var GROUND = 14;
// Map array
var map = [
[3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3],
[3,3,3,3,3,3,3,3,5,6,3,3,3,3,3,3,3,3,3,3,5,6,3,3],
[3,3,5,6,3,3,4,3,3,3,3,3,3,3,5,6,3,3,3,3,3,3,3,3],
[3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,9,3,3,3],
[3,7,7,3,3,3,3,3,3,3,3,3,3,3,3,3,7,7,7,7,7,7,3,3],
[3,3,3,3,3,3,3,3,3,7,3,3,3,3,3,3,3,3,3,3,3,3,3,3],
[3,3,3,7,7,7,3,3,3,3,3,3,7,7,3,3,3,3,3,3,3,4,3,3],
[3,3,3,3,3,3,3,3,5,6,3,3,3,3,3,3,3,3,3,3,3,3,3,3],
[3,3,4,3,3,3,3,3,3,3,3,3,4,3,3,7,7,7,7,7,3,3,3,3],
[3,3,3,3,3,7,7,7,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3],
[3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,4,3,3,3],
[3,3,3,3,3,3,3,3,3,3,3,7,7,7,7,3,3,3,3,3,3,3,3,3],
[3,3,2,3,3,3,3,3,3,3,2,3,3,3,3,3,2,3,3,3,2,3,3,3],
[14,14,1,14,14,14,14,14,14,14,1,14,14,14,14,14,1,14,14,14,1,14,14,14]
];
var gameObjects = [
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,8,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,13,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,12,0,0,0,0,0,0,0,8,12,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,12,0,8,0,0,0,0],
[0,0,0,0,0,10,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,11,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
];
// Cell size
var SIZE = 32;
// The number of rows and columns
var ROWS = map.length;
var COLS = map[0].length;
// Sprite object
var spriteObject =
{
sourceX: 0,
sourceY: 0,
sourceWidth: 32,
sourceHeight: 32,
width: 32,
height: 32,
x: 0,
y: 0,
vx: 0,
vy: 0,
visible: true,
//Getters
centerX: function()
{
return this.x + (this.width / 2);
},
centerY: function()
{
return this.y + (this.height / 2);
},
halfWidth: function()
{
return this.width / 2;
},
halfHeight: function()
{
return this.height / 2;
},
};
//arrays to store game objects
var sprites = [];
var eggs = [];
var dinos = [];
var platforms = [];
var assetsToLoad = [];
var assetsLoaded = 0;
//load the tilesheet
var image = new Image();
image.addEventListener("load", loadHandler, false);
image.src = "../images/spritesheet.png";
assetsToLoad.push(image);
//Game states
var LOADING = 0;
var BUILD_MAP = 1;
var PLAYING = 2;
var OVER = 3;
var gameState = LOADING;
// key codes
var LEFT = 37;
var RIGHT = 39;
var SPACE = 32;
// Directions
var moveLeft = false;
var moveRight = false;
window.addEventListener("keydown", function(event) {
switch(event.keyCode)
{
case LEFT:
moveLeft = true;
break;
case RIGHT:
moveRight = true;
break;
}}, false);
window.addEventListener("keyup", function(event) {
switch(event.keyCode)
{
case LEFT:
moveLeft = false;
break;
case RIGHT:
moveRight = false;
break;
}}, false);
update();
function update() {
requestAnimationFrame(update, canvas);
switch (gameState) {
case LOADING:
console.log("loading...");
break;
case BUILD_MAP:
buildMap(map);
buildMap(gameObjects);
gameState = PLAYING;
break;
case PLAYING:
playGame();
break;
case OVER:
endGame();
break;
}
render();
}
function loadHandler() {
assetsLoaded++;
if (assetsLoaded === assetsToLoad.length) {
image.removeEventListener("load", loadHandler, false);
gameState = BUILD_MAP;
}
}
function buildMap(map) {
for (var row=0; row < ROWS; row++) {
for (var col=0; col < COLS; col++) {
var currentTile = map[row] [col];
if (currentTile !== EMPTY) {
switch (currentTile) {
case GROUND:
var ground = Object.create(spriteObject);
ground.sourceX = 0;
ground.sourceY = 0;
ground.x = col * SIZE;
ground.y = row * SIZE;
sprites.push(ground);
break;
case TREE_BOTTOM:
var treeBottom = Object.create(spriteObject);
treeBottom.sourceX = 0;
treeBottom.sourceY = 32;
treeBottom.x = col * SIZE;
treeBottom.y = row * SIZE;
sprites.push(treeBottom);
break;
case TREE_TOP:
var treeTop = Object.create(spriteObject);
treeTop.sourceX = 0;
treeTop.sourceY = 64;
treeTop.x = col * SIZE;
treeTop.y = row * SIZE;
sprites.push(treeTop);
break;
case SKY:
var sky = Object.create(spriteObject);
sky.sourceX = 0;
sky.sourceY = 96;
sky.x = col * SIZE;
sky.y = row * SIZE;
sprites.push(sky);
break;
case CLOUD:
var cloud = Object.create(spriteObject);
cloud.sourceX = 0;
cloud.sourceY = 128;
cloud.x = col * SIZE;
cloud.y = row * SIZE;
sprites.push(cloud);
break;
case CLOUD_LEFT:
var cloudLeft = Object.create(spriteObject);
cloudLeft.sourceX = 0;
cloudLeft.sourceY = 160;
cloudLeft.x = col * SIZE;
cloudLeft.y = row * SIZE;
sprites.push(cloudLeft);
break;
case CLOUD_RIGHT:
var cloudRight = Object.create(spriteObject);
cloudRight.sourceX = 0;
cloudRight.sourceY = 192;
cloudRight.x = col * SIZE;
cloudRight.y = row * SIZE;
sprites.push(cloudRight);
break;
case PLATFORM:
var platform = Object.create(spriteObject);
platform.sourceX = 0;
platform.sourceY = 224;
platform.x = col * SIZE;
platform.y = row * SIZE;
sprites.push(platform);
platforms.push(platform);
break;
case CAVE:
var cave = Object.create(spriteObject);
cave.sourceX = 0;
cave.sourceY = 288;
cave.x = col * SIZE;
cave.y = row * SIZE;
sprites.push(cave);
break;
case EGG:
var egg = Object.create(spriteObject);
egg.sourceX = 0;
egg.sourceY = 256;
egg.x = col * SIZE;
egg.y = row * SIZE;
sprites.push(egg);
eggs.push(egg);
break;
case MEAT:
var meat = Object.create(spriteObject);
meat.sourceX = 0;
meat.sourceY = 320;
meat.x = col * SIZE;
meat.y = row * SIZE;
meat.visible = false;
sprites.push(meat);
break;
case DINO:
var dino = Object.create(spriteObject);
dino.sourceX = 0;
dino.sourceY = 416;
dino.x = col * SIZE;
dino.y = row * SIZE;
sprites.push(dino);
dinos.push(dino);
break;
case GUARD:
var guard = Object.create(spriteObject);
guard.sourceX = 0;
guard.sourceY = 480;
guard.x = col * SIZE;
guard.y = row * SIZE;
sprites.push(guard);
break;
case MAN:
var man = Object.create(spriteObject);
man.sourceX = 0;
man.sourceY = 352;
man.x = col * SIZE;
man.y = row * SIZE;
sprites.push(man);
break;
}
}
}
}
}
function playGame() {
if (moveLeft && !moveRight) {
man.vx = -3;
}
if (moveRight && !moveLeft) {
man.vx = 3;
}
if (!moveLeft && !moveRight) {
man.vx = 0;
}
man.x += man.vx;
}
function endGame() {
}
function render() {
drawingSurface.clearRect(0, 0, canvas.width, canvas.height);
if (sprites.length !== 0) {
for (i=0; i < sprites.length; i++) {
var sprite = sprites[i];
if (sprite.visible) {
drawingSurface.drawImage (
image,
sprite.sourceX, sprite.sourceY,
sprite.sourceWidth, sprite.sourceHeight,
Math.floor(sprite.x), Math.floor(sprite.y),
sprite.width, sprite.height
);
}
}
}
}
那是
因为man是在本地范围内。因此，playGame函数无法"看到"它。
要解决此问题，只需在 buildMap 函数之外声明变量（将"var man;"）声明（最好在它之前）。
我认为
看你的代码是....您已经声明了变量"man"，它是函数"buildMap"的本地变量
并且您正在尝试在另一个功能中访问它，即。"玩游戏"..
可能是这就是问题所在...
您可以通过使其全球化来解决它...在脚本的最顶行希望它有效。
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