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Select length 属性
定义和用法
length 属性可返回下拉列表中选项的数目。
语法
selectObject.length=number
浏览器支持
所有主要浏览器都支持 length 属性
实例
显示下拉列表的选项数目:
<html>
<head>
<script>
function displayResult()
{
alert(document.getElementById("mySelect").length);
}
</script>
</head>
<body>
<form>
<select id="mySelect">
<option>Apple</option>
<option>Pear</option>
<option>Banana</option>
<option>Orange</option>
</select>
</form>
<button type="button" onclick="displayResult()">How many options?</button>
</body>
</html>
<head>
<script>
function displayResult()
{
alert(document.getElementById("mySelect").length);
}
</script>
</head>
<body>
<form>
<select id="mySelect">
<option>Apple</option>
<option>Pear</option>
<option>Banana</option>
<option>Orange</option>
</select>
</form>
<button type="button" onclick="displayResult()">How many options?</button>
</body>
</html>