当我运行rails应用程序并在控制台中输入likeButton时，它会给我Uncaught ReferenceError:likeButton未定义在：1:1(匿名(@VM1591:1我试着将html中的脚本移动到head和body。我目前正在尝试使用DOMContentLoaded，但似乎遗漏了一些内容。我的总体目标是在按下按钮后更改按钮的颜色，并在页面刷新后保持颜色。我正在使用sessionStorage进行此过程。我只想确保在加载html之后声明likeButton变量。如果可能的话，只在javascript中完成。
//first js file
const BASE_URL = "http://localhost:3000"
const GPUS_URL = `${BASE_URL}/gpus`
const USERS_URL = `${BASE_URL}/users`
const gpuCollection = document.querySelector('#gpu-collection')
let wish = sessionStorage.getItem('wish');
class Gpu {
constructor(gpuAttributes) {
this.title = gpuAttributes.title;
this.price = gpuAttributes.price;
this.features = gpuAttributes.features;
this.link = gpuAttributes.link;
this.image = gpuAttributes.image;
this.id = gpuAttributes.id;
}
render() {
let div = document.createElement('div');
div.classList.add('card');
let h = document.createElement('h2');
let t = document.createTextNode(`${this.title} ($${this.price})`);
h.appendChild(t);
div.appendChild(h);
let h1 = document.createElement('h1');
h1.classList.add('gpu-cat');
h1.innerHTML = `${this.features}`;
div.appendChild(h1);
let button = document.createElement('button');
button.classList.add('list_btn');
button.innerHTML = '♡';
div.appendChild(button);
let a = document.createElement('a');
let img = document.createElement('img');
a.href = `${this.link}`;
a.target = '_blank';
img.src = `${this.image}`;
img.classList.add('gpu-image');
a.appendChild(img);
div.appendChild(a);
gpuCollection.appendChild(div);
}
}
//second js file
document.addEventListener("DOMContentLoaded", function (){
let likeButton;
SignUp();
logInUser();
logOutUser();
function putGpusOnDom(gpuArray){
gpuArray.forEach(gpu => {
let newGpu = new Gpu(gpu)
newGpu.render()
});
likeButton = document.querySelector("button");
}
function fetchGpus(){
fetch(GPUS_URL)
.then(res => res.json())
.then(gpus => putGpusOnDom(gpus))
}
const enableWish = () => {
console.log(likeButton)
sessionStorage.setItem('wish', 'red')
}
gpuCollection.addEventListener('click', function (){
wish = sessionStorage.getItem('wish');
if(wish !== 'red'){
enableWish();
}else{
disableWish();
}
});
})
//html file
...
<body>
<div id = "gpu-collection"></div>
<script type="text/javascript" src="src/Gpu.js"></script>
<script type="text/javascript" src="src/index.js" ></script>
</body>
</html>
正如我在评论中提到的，如果动态添加，则like按钮在DOMContentLoaded上不可用。您需要等待按钮被放置在DOM 中
使用以下内容，我在这里进行一些猜测，因为您的代码中存在一些空白
document.addEventListener("DOMContentLoaded", function (){
//document.querySelector("button"); not yet available
//NOTE: The likeButton variable will ONLY be in scope INSIDE the event listener function
// You will not be able to access directly in the console.
let likeButton;
SignUp();
logInUser();
logOutUser();
function putGpusOnDom(gpuArray){
gpuArray.forEach(gpu => {
let newGpu = new Gpu(gpu)
newGpu.render()
});
//Now you have rendered the button it is available
//CAUTION: querySelector("button") will grab the first button on the page
// and ONLY the first button
likeButton = document.querySelector("button");
//Log like button to console while it is still in scope.
console.log(likeButton);
}
function fetchGpus(){
fetch(GPUS_URL)
.then(res => res.json())
.then(gpus => putGpusOnDom(gpus))
}
const enableWish = () => {
console.log(likeButton)
sessionStorage.setItem('wish', 'red')
}
})