[英]JavaScript - dropdown validation selection
I have 3 dropdowns
, I would like to check in JavaScript that at least one selection has been made, if not display a message. 我有3个
dropdowns
,如果没有显示消息,我想签入JavaScript至少进行了一次选择。 What would be the simplest way to do it in JavaScript? 用JavaScript做到这一点的最简单方法是什么?
id: dropdown1 id: dropdown2 id: dropdown3 id:dropdown1 id:dropdown2 id:dropdown3
Thanks 谢谢
// need to make sure the first dropdown option is blank, then... //需要确保第一个下拉选项为空白,然后...
var dd1 = document.getElementById('dropdown1'); var dd1 = document.getElementById('dropdown1');
var dd2 = document.getElementById('dropdown2'); var dd2 = document.getElementById('dropdown2');
var dd3 = document.getElementById('dropdown3'); var dd3 = document.getElementById('dropdown3');
if (
(dd1.selectedIndex == 0) &&
(dd2.selectedIndex == 0) &&
(dd3.selectedIndex == 0)
) {
alert('need to select at least one')
}
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