如何检查下拉列表在jQuery中是否有一个值? [英] How to check if dropdown has one value or none in jquery?

问题描述

我想做的是检查下拉列表中是否有一个值或没有一个值，然后将其设为只读?

What I want to do is check if a drop down has one value or none and then make it read only?

if(){
 $('#dropdown').attr("disabled", "disabled");
}


<select class="dropdown" name="dropdown" id="dropdown">
        <option value="L6.5">L6.5</option>
   </select> 

<select class="dropdown" name="dropdown2" id="dropdown2"></select>


<select class="dropinput" name="dropdown3" id="dropdown3">
       <option value=""></option>
       <option value=""></option>
</select>

我需要禁用前三个下拉菜单

I need all top three dropdowns to be disabled

推荐答案

根据HTML规范，HTML中的select标签没有只读属性，只有禁用的属性.尝试此操作，它将检查一个或否选项，并相应地disable进行检查.

According to HTML specs, the select tag in HTML doesn't have a readonly attribute, only a disabled attribute. Try this it will check for one or no option and disable it accordingly.

var $dd = $('#dropdown');
if($dd.find('option').length <= 1){
    $dd.prop('disabled', true);    
}
else{
    $dd.prop('disabled', false); 
}

演示

Demo

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