本文通过一个简单的HTML页面示例展示了如何使用JavaScript处理onchange事件。当用户从下拉菜单中选择不同的颜色选项时，该事件会触发背景颜色的变化，并在页面上显示相应的文字反馈。
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>onchange()</title>
<style type="text/css">
#div {
width: 300px;
height: 300px;
border: 2px solid gray;
margin: 100px 0 0 200px;
}
</style>
<script type="text/javascript">
window.onload = changcolor;
function changcolor() {
var a = document.getElementById('color');
var b = document.getElementById('div');
a.onchange = function() {
if (this.value == 0) {
b.innerHTML = "我没有发生任何变化";
} else {
b.style.background = this.value;
b.innerHTML = "我的颜色变成" + this.value;
}
}
}
</script>
</head>
<body>
<div>
<span>请选择您喜欢的颜色:</span>
<select id="color">
<option value="0">请选择</option>
<option value="yellow">黄色</option>
<option value="orange">橘色</option>
<option value="pink">粉色</option>
<option value="purple">紫色</option>
</select>
</div>
<div id="div">我是div</div>
</body>
</html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>onchange()</title>
<style type="text/css">
#div {
width: 300px;
height: 300px;
border: 2px solid gray;
margin: 100px 0 0 200px;
}
</style>
<script type="text/javascript">
window.onload = changcolor;
function changcolor() {
var a = document.getElementById('color');
var b = document.getElementById('div');
a.onchange = function() {
if (this.value == 0) {
b.innerHTML = "我没有发生任何变化";
} else {
b.style.background = this.value;
b.innerHTML = "我的颜色变成" + this.value;
}
}
}
</script>
</head>
<body>
<div>
<span>请选择您喜欢的颜色:</span>
<select id="color">
<option value="0">请选择</option>
<option value="yellow">黄色</option>
<option value="orange">橘色</option>
<option value="pink">粉色</option>
<option value="purple">紫色</option>
</select>
</div>
<div id="div">我是div</div>
</body>
</html>
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