javascript - 如何使用 javascript 更改选项标签上的 "selected"属性

Question

我正在为在线订单创建一个网络表单。我想使用 javaScript 将选择框默认为当前月份，但它似乎对我不起作用，我不确定为什么。我是 javascript 新手，但我想我已经弄清楚了。我是否遗漏了什么或误解了什么？这是 HTML:

<label for="orderMonth">Month</label>
            <select name="month" id="orderMonth" onchange="setselect()">
                <option value="01" id="m0">January</option>
                <option value="02" id="m1">February</option>
                <option value="03" id="m2">March</option>
                <option value="04" id="m3">Aprl</option>
                <option value="05" id="m4">May</option>
                <option value="06" id="m5">June</option>
                <option value="07" id="m6">July</option>
                <option value="08" id="m7">August</option>
                <option value="09" id="m8">September</option>
                <option value="10" id="m9">October</option>
                <option value="11" id="m10">November</option>
                <option value="12" id="m11">December</option>
            </select>

这是我尝试的第一种脚本:

<script>
        var month = getMonth();
        var opt = document.getElementById("m"+month);
        opt.setAttribute("selected");
    </script>

我尝试的第二种方法:

<script>
        var month = getMonth();
        if (month == 0) {
            document.getElementById("m0").selected = true;}
        else if (month == 1) {
            document.getElementById("m1").selected = true;}
        else if (month == 2) {
            document.getElementById("m2").selected = true;}
        else if (month == 3) {
            document.getElementById("m3").selected = true;}
        else if (month == 4) {
            document.getElementById("m4").selected = true;}
        else if (month == 5) {
            document.getElementById("m5").selected = true;}
        else if (month == 6) {
            document.getElementById("m6").selected = true;}
        else if (month == 7) {
            document.getElementById("m7").selected = true;}
        else if (month == 8) {
            document.getElementById("m8").selected = true;}
        else if (month == 9) {
            document.getElementById("m9").selected = true;}
        else if (month == 10) {
            document.getElementById("m10").selected = true;}
        else if(month == 11) {
            document.getElementById("m11").selected = true;}
    </script>

有人有什么想法吗？

Answer 1

您必须创建一个新的 Date 对象来获取月份。请看下面的代码:

var today=new Date();
var month = today.getMonth();
        if (month == 0) {
            document.getElementById("m0").selected = true;}
        else if (month == 1) {
            document.getElementById("m1").selected = true;}
        else if (month == 2) {
            document.getElementById("m2").selected = true;}
        else if (month == 3) {
            document.getElementById("m3").selected = true;}
        else if (month == 4) {
            document.getElementById("m4").selected = true;}
        else if (month == 5) {
            document.getElementById("m5").selected = true;}
        else if (month == 6) {
            document.getElementById("m6").selected = true;}
        else if (month == 7) {
            document.getElementById("m7").selected = true;}
        else if (month == 8) {
            document.getElementById("m8").selected = true;}
        else if (month == 9) {
            document.getElementById("m9").selected = true;}
        else if (month == 10) {
            document.getElementById("m10").selected = true;}
        else if(month == 11) {
            document.getElementById("m11").selected = true;}