<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body>
<button>识别鲤鱼</button><br><br>
<button>去掉</button><br><br>
<select id="sel" multiple>
<option value="0">香蕉</option>
<option value="1">苹果</option>
<option value="2" selected="">鲤鱼</option>
<option value="3">鸭梨</option>
</select>
<script>
//需求：点击识别水产，立刻把option对应的鲤鱼选择的属性设置为selected;
//步骤：
//1.获取事件源和相关元素
//2.绑定事件
//3.书写事件驱动程序
//1.获取事件源和相关元素
var btn1 = document.getElementsByTagName("button")[0];
var btn2 = document.getElementsByTagName("button")[1];
var sel = document.getElementById("sel");
var optArr = sel.getElementsByTagName("option");
//2.绑定事件
btn1.onclick = function () {
//3.书写事件驱动程序
optArr[2].selected = true;
}
btn2.onclick = function () {
//3.书写事件驱动程序
optArr[2].selected = false;
optArr[3].selected = true;
}
</script>
</body>
</html>
selected
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