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网页编程－添加与删除Option对象

<script language="JavaScript">
// 添加选项
function addOption(pos){
    var objSelect = document.myForm.mySelect;
    // 取得字段值
    var strName = document.myForm.myOptionName.value;
    var strValue = document.myForm.myOptionValue.value;
    // 建立Option对象
    var objOption = new Option(strName,strValue);
    if (pos == -1 & pos > objSelect.options.length) 
       objSelect.options[objSelect.options.length] = objOption;
    else
       objSelect.add(objOption, pos);
}
// 删除选项
function deleteOption(type){
    var objSelect = document.myForm.mySelect;
    if (type == true)
       objSelect.options[objSelect.selectedIndex] = null;
    else
       objSelect.remove(objSelect.selectedIndex);
}
// 显示选项信息
function showOption(objForm){
    var objSelect = objForm.mySelect;
    var name = objSelect.options[objSelect.selectedIndex].text;
    var value = objSelect.options[objSelect.selectedIndex].value;
    alert(name + " = " + value);
}
</script>
</head>
<body>
<h2>添加与删除Option对象</h2>
<hr>
<form name="myForm">
<select name="mySelect">
<option value="中国" Selected>中国</option>
<option value="日本">日本</option>
<option value="美国">美国</option>
</select>
<input type="button" onclick="showOption(this.form)" value="显示">
<input type="button" onclick="deleteOption(true)" value="删除">
<input type="button" onclick="deleteOption(false)" value="Remove方法"><br><br>
选项名称 : <input type="text" name="myOptionName" value="英国"><br>
选项的值 : <input type="text" name="myOptionValue" value="value4">
<input type="button" onclick="addOption(-1)" value="添加">
<input type="button" onclick="addOption(0)" value="插入">
</form>