不允许我设置Javascript创建的div的类名

Question

我正在使用一个函数在页面上创建一个div元素。我想分配一个类名，但收到错误：无法设置属性类名未定义。

但我在另一个功能中这样做了，它奏效了。为什么这个不起作用？

如果我未能提供与问题相关的代码，我深表歉意。我很着急，并包含了我认为可能按相关性顺序相关的代码。

** 工作功能 **

function makeBomb() {
if (player.ready && (player.hasBomb < player.maxBombs)) {
player.score -= 300;
player.hasBomb++;
player.bomb = document.createElement('div');
player.bomb.className = 'bomb'; //DOESN'T THROW ERROR ----
gameArea.appendChild(player.bomb);
player.bomb.x = player.x;
player.bomb.y = player.y;
player.bomb.style.left = player.bomb.x + 'px';
player.bomb.style.top = player.bomb.y + 'px';
player.ready = false;
setTimeout(function () {
player.ready = true;
}, 1000);
}
}

**功能不工作 **

function makeBullet() {
if (player.enemy.bulletCount < player.enemy.maxBulletCount && 
player.enemy.bulletInterval == true)
player.enemy.bullet = document.createElement('div');
player.enemy.bullet.className = 'bullet';  //THROWS ERROR -----
gameArea.appendChild(player.enemy.bullet);
player.enemy.bullet.x = player.enemy.x;
player.enemy.bullet.y = player.enemy.y;
player.enemy.bullet.style.left = player.enemy.bullet.x + 
(player.enemy.offsetWidth / 3) + 'px';
player.enemy.bullet.style.top = player.enemy.bullet.y + 
(player.enemy.offsetHeight / 4) + 'px';
player.enemy.bulletCount++;
player.enemy.bulletInterval = false;
setInterval(function(){
player.enemy.bulletInterval = true;
}, 4000);
}

** 可能具有上下文 IDK 的起始代码**

function start() {
if (player.games === 1) {
gameArea.removeChild(finalScore);
}
gameMessage.style.display = 'none';
score.style.display = "inline-block";
scoreArea.style.display = "inline-block";
text.style.display = "inline-block";
player.inplay = true;
makeEnemy();
player.plane = document.createElement("div");
player.plane.setAttribute("class", "plane");
gameArea.appendChild(player.plane);
player.enemy.x = player.enemy.offsetLeft;
player.enemy.y = player.enemy.offsetTop;
player.x = player.plane.offsetLeft;
player.y = player.plane.offsetTop;

window.requestAnimationFrame(playGame);

}

**可能具有上下文的其他代码 **

function makeEnemy() {
player.enemy = document.createElement('div');
player.enemy.className = 'enemy';
player.enemy.style.left = Math.floor(Math.random() * . 
gameArea.offsetWidth - 300) + 100 + 'px';

gameArea.appendChild(player.enemy);
player.enemy.x = player.enemy.offsetLeft;
}

**以防万一你需要 - idk我很难跟踪可能与问题相关的所有内容......不好意思。。**

title.addEventListener("click", changeColor);
const gameArea = document.querySelector(".gameArea");
const game = document.querySelector(".game");
const scoreArea = document.querySelector(".scoreArea");
const score = document.querySelector(".score");
const text = document.querySelector(".text");

document.addEventListener('keydown', pressOn);
document.addEventListener('keyup', pressOff);
gameMessage.addEventListener('click', start);
let player = {
score: 2000,
speed: 5,
inplay: false,
ready: true,
maxBombs: 4,
hasBomb: 0,
hit: 0,
hitMax: 9,
games: 0,
enemy: {
x: 0
},
getHit: 0,
getHitMax: 20,
swing: false
}
let keys = {
space: false
}

**完整的JS文件：警告我非常新，这不是好的代码**

const title = document.querySelector(".title");
const gameMessage = document.querySelector(".gameMessage");

function changeColor() {
let newArray = ["darksalmon", "lightsalmon", "crimson", "red", "deeppink", "yellowgreen", "ghostwhite"];
let random = Math.floor(Math.random() * Math.floor(newArray.length - 1));
if (title.style.color != newArray[random]) {
title.style.color = newArray[random];
console.log(title.style.color);
} else {
changeColor();
}
}

title.addEventListener("click", changeColor);
const gameArea = document.querySelector(".gameArea");
const game = document.querySelector(".game");
const scoreArea = document.querySelector(".scoreArea");
const score = document.querySelector(".score");
const text = document.querySelector(".text");

document.addEventListener('keydown', pressOn);
document.addEventListener('keyup', pressOff);
gameMessage.addEventListener('click', start);
let player = {
score: 2000,
speed: 5,
inplay: false,
ready: true,
maxBombs: 4,
hasBomb: 0,
hit: 0,
hitMax: 9,
games: 0,
enemy: {
x: 0
},
getHit: 0,
getHitMax: 20,
swing: false
}
let keys = {
space: false
}
function start() {
if (player.games === 1) {
gameArea.removeChild(finalScore);
}
gameMessage.style.display = 'none';
score.style.display = "inline-block";
scoreArea.style.display = "inline-block";
text.style.display = "inline-block";
player.inplay = true;
makeEnemy();
player.plane = document.createElement("div");
player.plane.setAttribute("class", "plane");
gameArea.appendChild(player.plane);
player.enemy.x = player.enemy.offsetLeft;
player.enemy.y = player.enemy.offsetTop;
player.x = player.plane.offsetLeft;
player.y = player.plane.offsetTop;

window.requestAnimationFrame(playGame);

}

function playGame() {
if (player.inplay) {
moveBomb();
if(player.x < (gameArea.offsetWidth / 2)) {
console.log('WORKED');
makeBullet();
}
if (player.swing){
player.plane.style.backgroundImage ='url(guts1.png)';
player.swing = false;
//player.plane.style.width = 210 + 'px';
}

if (keys['x'] && player.enemy && isCollide(player.plane, player.enemy)) {
removeEnemy();
}

if (player.enemy) {

if (isCollide(player.plane, player.enemy)) {

player.getHit++;
if (player.getHit > player.getHitMax){
endGame();
}    
} else {
player.getHit = 0;
}
if (player.x > player.enemy.x) {
player.enemy.x += 1;
}
if (player.x < player.enemy.x) {
player.enemy.x -= 1;
}
player.enemy.style.left = player.enemy.x + 'px';
}
if (player.hasBomb >= player.maxBombs && player.bomb.y > gameArea.offsetHeight - 20) {
endGame();
}
if (keys.space) {
makeBomb()
}
if (keys.ArrowUp && player.y > 0) {
player.y -= (player.speed + (player.speed * .5));
}
if (keys.ArrowDown && player.y < (gameArea.offsetHeight - player.plane.offsetHeight - 30)) {
player.y += (player.speed + (player.speed * .5));
}
if (keys.ArrowLeft && player.x > 0) {
player.x -= (player.speed + (player.speed * .5));
}
if (keys.ArrowRight && player.x < (gameArea.offsetWidth)) {
player.x += (player.speed - (player.speed * .5));
}
if (player.x == (gameArea.offsetWidth)) {
player.x = 0;
player.score -= 100;
if (!player.enemy) {
makeEnemy();
}
}
player.score -= .4;
if (player.score < 0) {
player.score = 0;
}
player.x += (player.speed * .5);

score.innerHTML = Math.floor(player.score) + ' Bombs left: ' + (player.maxBombs - player.hasBomb);

player.plane.style.left = player.x + 'px';
player.plane.style.top = player.y + 'px';
window.requestAnimationFrame(playGame);
}
}
function pressOn(e) {
e.preventDefault();
let tempKey = (e.key == " ") ? "space" : e.key;
keys[tempKey] = true;
if (keys['x'] && player.swing == false){
playerPlane = player.plane;
player.plane.style.backgroundImage ='url(guts2.png)';
setTimeout(function () {
player.swing = true;
}, 300);
//player.plane.style.width = 400 + 'px';
}
console.log(tempKey)
console.log(keys);
}
function pressOff(e) {
e.preventDefault();
let tempKey = (e.key== " ") ? "space" : e.key;
console.log(tempKey);
//    if (keys['x'] && player.swing){
//               playerPlane = player.plane;
//               player.plane.style.backgroundImage ='url(guts1.png)';
//                 player.swing = false;
//                 //player.plane.style.width = 210 + 'px';
//              
//              }
if (keys['space'] || keys['x']) {
keys['space'] = 0;
keys['x'] = 0;
}
keys[tempKey] = false;
console.log(keys);
}
function moveBomb() {
let bombs = document.querySelectorAll('.bomb');
bombs.forEach(function (item) {
item.y += 10;
item.style.top = item.y + 'px';
if (item.y > gameArea.offsetHeight) {
item.parentNode.removeChild(item);
player.bomb = null;
}
if (player.enemy && player.bomb) {
if (isCollide(item, player.enemy)) {
player.hit++;
}
}
if (player.hit > player.hitMax) {
item.parentNode.removeChild(item);
player.bomb = null;
player.score += 2000;
player.hit = 0;
player.hasBomb -= 2
gameArea.removeChild(player.enemy);
player.enemy = null;
}
})
}
function makeEnemy() {
player.enemy = document.createElement('div');
player.enemy.className = 'enemy';
player.enemy.style.left = Math.floor(Math.random() * gameArea.offsetWidth - 300) + 100 + 'px';

gameArea.appendChild(player.enemy);
player.enemy.x = player.enemy.offsetLeft;
}
//function getLocationX(a){
//    let aRect = a.getBoundingClientRect();
//    let aX = aRect.x;
//    return aX;
//   //w console.log(aX);
//}
//
//function getLocationY(a){
//    let aRect = a.getBoundingClientRect();
//    let aY = aRect.y;
//    return aY;
//   // console.log(aY);
//}
function isCollide(a, b) {
let aRect = a.getBoundingClientRect();
let bRect = b.getBoundingClientRect();
return !(
(aRect.bottom < bRect.top) ||
(aRect.top > bRect.bottom) ||
(aRect.right < bRect.left) ||
(aRect.left > bRect.right)
)
}
function makeBomb() {
if (player.ready && (player.hasBomb < player.maxBombs)) {
player.score -= 300;
player.hasBomb++;
player.bomb = document.createElement('div');
player.bomb.className = 'bomb';
gameArea.appendChild(player.bomb);
player.bomb.x = player.x;
player.bomb.y = player.y;
player.bomb.style.left = player.bomb.x + 'px';
player.bomb.style.top = player.bomb.y + 'px';
player.ready = false;
setTimeout(function () {
player.ready = true;
}, 1000);
}
}

function makeBullet() {
if (player.enemy.bulletCount < player.enemy.maxBulletCount && player.enemy.bulletInterval == true)
player.enemy.bullet = document.createElement('div');
player.enemy.bullet.className = 'bullet';
gameArea.appendChild(player.enemy.bullet);
player.enemy.bullet.x = player.enemy.x;
player.enemy.bullet.y = player.enemy.y;
player.enemy.bullet.style.left = player.enemy.bullet.x + (player.enemy.offsetWidth / 3) + 'px';
player.enemy.bullet.style.top = player.enemy.bullet.y + (player.enemy.offsetHeight / 4) + 'px';
player.enemy.bulletCount++;
player.enemy.bulletInterval = false;
setInterval(function(){
player.enemy.bulletInterval = true;
}, 4000);
}
function endGame() {
if (player.enemy) {
gameArea.removeChild(player.enemy);
}
gameArea.removeChild(player.plane);
if (player.bomb){
gameArea.removeChild(player.bomb);
player.bomb = null;
}
score.style.display = 'none';
scoreArea.style.display = 'none';
text.style.display = 'none';
gameMessage.style.display = 'inline-block';
player.inplay = false;
player.hasBomb = 0;
finalScore = document.createElement('div');
finalScore.classList.add('finalScore');
finalScore.innerHTML = 'YOU SCORED: ' + Math.floor(player.score);
gameArea.appendChild(finalScore);
player.games = 1;
player.getHit = 0;
}
function removeEnemy() {
gameArea.removeChild(player.enemy);
player.enemy = null;
player.score += 2000;
}

Answer 1

function makeBullet() {
if (player.enemy.bulletCount < player.enemy.maxBulletCount && 
player.enemy.bulletInterval == true)

您在 if 语句末尾缺少大括号，我认为它将下一行解释为单行 if 语句的一部分

更改为

function makeBullet() {
if (player.enemy.bulletCount < player.enemy.maxBulletCount && 
player.enemy.bulletInterval == true) {
...
...
...
}
}