HTML <选择>JQuery .change 不起作用 [英] HTML &lt;select&gt; JQuery .change not working

问题描述

好吧，我不明白为什么这不起作用.看起来很简单.

这是我的下拉菜单:

<表格><select id='yearDropdown'><c:forEach var="years" items="${parkYears}"><option value=/events.html?display_year=${years}<c:if test="${currentYear == years}">selected="selected"</c:if>>${年}</c:forEach></选择></表单>

这里是 JavaScript

$("#yearDropdown").change(function () {alert('带有值的选项' + $(this).val());});

现在我只想让它工作，这样我就可以添加功能.谢谢！

解决方案

该代码在语法上是正确的.很可能在错误的时间运行它.

您需要在 DOM 就绪时绑定事件:

---

原生 JS/DOM

window.addEventListener('DOMContentLoaded', () => {const yearDropDown = document.getElementById('yearDropdown');yearDropDown.addEventListener('change', () => {警报(yearDropDown.value)});});

---

jQuery

$(function(){/* DOM 就绪 */$("#yearDropdown").change(function() {alert('带有值的选项' + $(this).val());});});

或者，使用live:

$("#yearDropdown").live('change', function() {alert('带有值的选项' + $(this).val());});

或者，使用delegate:

$(document.body).delegate('#yearDropdown', 'change', function() {alert('带有值的选项' + $(this).val());});

或者，如果您使用的是 jQuery 1.7+:

$("#yearDropdown").on('change', function() {alert('带有值的选项' + $(this).val());});

---

尽管如此，通常最好在浏览器完成标记渲染后执行脚本.

Alright I don't see why this isnt working. It seems pretty simple.

Here is my drop-down menu:

<div>
    <form>
        <select id='yearDropdown'>
            <c:forEach var="years" items="${parkYears}">
                <option value=/events.html?display_year=${years}<c:if test="${currentYear == years}">selected="selected"</c:if>>${years}</option>
            </c:forEach>
        </select>
    </form>
</div>

and here is the JavaScript

$("#yearDropdown").change(function () {
    alert('The option with value ' + $(this).val());
});

Right now I just want to get it working so I can add functionality. Thanks!

解决方案

That code is syntactically correct. Most likely running it at the wrong time.

You'll want to bind the event when the DOM is ready:

---

Native JS/DOM

window.addEventListener('DOMContentLoaded', () => {
    const yearDropDown = document.getElementById('yearDropdown');
    yearDropDown.addEventListener('change', () => { 
        alert(yearDropDown.value)
    });
});

---

jQuery

$(function(){ /* DOM ready */
    $("#yearDropdown").change(function() {
        alert('The option with value ' + $(this).val());
    });
});

Or, use live:

$("#yearDropdown").live('change', function() {
    alert('The option with value ' + $(this).val());
});

Or, use delegate:

$(document.body).delegate('#yearDropdown', 'change', function() {
    alert('The option with value ' + $(this).val());
});

Or, if you're using jQuery 1.7+:

$("#yearDropdown").on('change', function() {
    alert('The option with value ' + $(this).val());
});

---

Nonetheless, it is usually best to execute script once the browser has finished rendering Markup.

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