使用 list.forEach() 添加事件侦听器 - 仅更改最后一个列表项

Question

我是网页设计（和编码）的新手，今天下午我遇到了一个我无法独自解决的问题。我希望你们中的一个能帮助我。

我想创建当用户将鼠标悬停在其上时变为绿色，当鼠标再次离开时变为红色的文本元素。（稍后，当鼠标悬停在特定对象上时，音频文件将开始播放。）当您运行代码时，您可以看到只有最后一个元素变为红色，当鼠标悬停在其他元素上时也是如此。我的 (Javascript) 代码有什么问题？

const elements = [
    {title: 'Element1'},
    {title: 'Element2'},
    {title: 'Element3'},
    {title: 'Element4'},
    {title: 'Element5'}
];

window.onload = () => {
    elements.forEach(element => {
        title = document.getElementById(element.title);
        //add event listeners
        title.addEventListener("mouseover", handleMouseOver = () => {
            mouseOver(title);
        });
        title.addEventListener("mouseout", handleMouseOut = () => {
            mouseOut(title);
        });
    });
};

//play soundfiles
const mouseOver = (title) => {
    title.style.backgroundColor = "red";
};
const mouseOut = (title) => {
    title.style.backgroundColor = "#4CAF50";
};

body {
    margin:0;
          margin-left:0em;
          padding:0;
          overflow: hidden;
      }
      canvas {
          margin:auto;
      }

.compositions {
    display: inline-block;
    align-items: center;
    font-style: arial;
    font-size: 17px;
    list-style-type: none;
    text-align: center;
    margin-top: 5em;
}
.compositions p {
    margin-bottom: 0.8em;
    margin:0em 0.8em 1em 1em;
    display: inline-block;
}

.compositions input {
    background-color: #4CAF50; /* Green */
    border: none;
    border-radius:50px;
    color: white;
    padding: 8px 20px;
    margin-left: 10px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-style: arial;
    font-size: 12px;
}

.compositions p:hover{
    font-weight: bold;
}

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <title>InteractiveWebsite</title>

    <script src="../libraries/p5.js"></script>
    <script src="../libraries/p5.dom.js"></script>
    <script src="../libraries/p5.sound.js"></script>
    <!--script src="../libraries/Tone.js"></script-->
    <!--CreateJS libraries-->
    <script src="../libraries/soundjs.min.js"></script>
    <script src="../libraries/cordovaaudioplugin.min.js"></script>
    <script src="../libraries/flashaudioplugin.min.js"></script>
    <script src="../libraries/preloadjs.min.js"></script>
    <!--Own javascript files-->

    <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
    <main>
        <div class="compositions">
            <p id=Element1>Element 1</p><br>
            <p id=Element2>Element 2</p><br>
            <p id=Element3>Element 3</p><br>
            <p id=Element4>Element 4</p><br>
            <p id=Element5>Element 5</p><br>
        </div>
    </main>
    <script src="sketch.js"></script>
    <noscript>Sorry, your browser does not support JavaScript!</noscript>
</body>
</html>

我研究了另外两个主题 ( and here)，但它们似乎不适合我的情况。

提前致谢，芥末整形器

Answer 1

您遇到关闭问题，标题未声明

window.onload = () => {
    elements.forEach(element => {
        title = document.getElementById(element.title);
        //add event listeners
        title.addEventListener("mouseover", handleMouseOver = () => {
            mouseOver(title);
        });
        title.addEventListener("mouseout", handleMouseOut = () => {
            mouseOut(title);
        });
    });
}

所以 'default declaration' 似乎在 forEach 之外。只需像 const title = document.getElementById(element.title); 一样声明它，一切都会起作用。

也为 id 属性添加引号，例如

            <p id='Element1'>Element 1</p><br>

这不是你的错误的一部分，只是一个小错误

版本

如您所见，它有效

const elements = [
    {title: 'Element1'},
    {title: 'Element2'},
    {title: 'Element3'},
    {title: 'Element4'},
    {title: 'Element5'}
];

window.onload = () => {
    elements.forEach(element => {
        const title = document.getElementById(element.title);
        //add event listeners
        title.addEventListener("mouseover", handleMouseOver = () => {
            mouseOver(title);
        });
        title.addEventListener("mouseout", handleMouseOut = () => {
            mouseOut(title);
        });
    });
};

//play soundfiles
const mouseOver = (title) => {
    title.style.backgroundColor = "red";
};
const mouseOut = (title) => {
    title.style.backgroundColor = "#4CAF50";
};

body {
    margin:0;
          margin-left:0em;
          padding:0;
          overflow: hidden;
      }
      canvas {
          margin:auto;
      }

.compositions {
    display: inline-block;
    align-items: center;
    font-style: arial;
    font-size: 17px;
    list-style-type: none;
    text-align: center;
    margin-top: 5em;
}
.compositions p {
    margin-bottom: 0.8em;
    margin:0em 0.8em 1em 1em;
    display: inline-block;
}

.compositions input {
    background-color: #4CAF50; /* Green */
    border: none;
    border-radius:50px;
    color: white;
    padding: 8px 20px;
    margin-left: 10px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-style: arial;
    font-size: 12px;
}

.compositions p:hover{
    font-weight: bold;
}

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <title>InteractiveWebsite</title>

    <script src="../libraries/p5.js"></script>
    <script src="../libraries/p5.dom.js"></script>
    <script src="../libraries/p5.sound.js"></script>
    <!--script src="../libraries/Tone.js"></script-->
    <!--CreateJS libraries-->
    <script src="../libraries/soundjs.min.js"></script>
    <script src="../libraries/cordovaaudioplugin.min.js"></script>
    <script src="../libraries/flashaudioplugin.min.js"></script>
    <script src="../libraries/preloadjs.min.js"></script>
    <!--Own javascript files-->

    <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
    <main>
        <div class="compositions">
            <p id='Element1'>Element 1</p><br>
            <p id='Element2'>Element 2</p><br>
            <p id='Element3'>Element 3</p><br>
            <p id='Element4'>Element 4</p><br>
            <p id='Element5'>Element 5</p><br>
        </div>
    </main>
    <script src="sketch.js"></script>
    <noscript>Sorry, your browser does not support JavaScript!</noscript>
</body>
</html>

Answer 2

我知道您稍后需要播放音频文件，但是当您可能 solve the problem with CSS 时，这是一项非常繁重的工作。通常，您不想用 JavaScript 做您可以用 CSS 做的事。为 CSS.

做不到的事情保存 JavaScript

p {
  background-color: #4CAF50;
}
p:hover {
  background-color: red;
}

使用 list.forEach() 添加事件侦听器 - 仅更改最后一个列表项

adding event listeners with list.forEach() - only last list item changes

javascript

event-handling

interactive