如何检查是否从 HTML 下拉列表中选择了一个项目? [英] How to check if an item is selected from an HTML drop down list?

问题描述

我有一个下拉列表，但无法检查是否从下拉列表中选择了一个值

I have a drop drown list and I am having trouble checking whether or not a value has been selected from the drop down list

下面是我的 HTML 代码:

Below is my HTML Code :

<label class="paylabel" for="cardtype">Card Type:</label>
<select id="cardtype" name="cards">
    <option value="selectcard">--- Please select ---</option>
    <option value="mastercard">Mastercard</option>
    <option value="maestro">Maestro</option>
    <option value="solo">Solo (UK only)</option>
    <option value="visaelectron">Visa Electron</option>
    <option value="visadebit">Visa Debit</option>
</select><br/>

下面是我的 JavaScript 代码:

Below is my JavaScript Code :

var card = document.getElementByName("cards")[0].value;
if (card.value == selectcard) {
    alert("Please select a card type");
}

推荐答案

好吧，您在字符串 selectcard 周围遗漏了引号，它应该是 "selectcard"

Well you missed quotation mark around your string selectcard it should be "selectcard"

if (card.value == selectcard)

应该是

if (card.value == "selectcard")

这里是完整的代码

function validate()
{
 var ddl = document.getElementById("cardtype");
 var selectedValue = ddl.options[ddl.selectedIndex].value;
    if (selectedValue == "selectcard")
   {
    alert("Please select a card type");
   }
}

JS 小提琴演示

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