从多个选择列表中获取未选择的选项 [英] get unselected option from multiple select list

问题描述

我有一个多重选择列表.当用户取消选择所选选项时，我想知道用户做出的未选择选项的值.我该如何捕捉?

I have a multiple select list. When user unselects the selected option, I want to know the value of the unselected option made by user. How do I capture it?

我的示例代码如下.

<select multiple>
    <option value="volvo">Volvo</option>
    <option value="saab">Saab</option>
    <option value="opel">Opel</option>
    <option value="audi">Audi</option>
</select> 

我有以下jquery代码，允许用户选择多个选项

I have following jquery code to allow user to select multiple options

$('option').mousedown(function(){ 
    e.preventDefault();
    $(this).prop('selected', $(this).prop('selected') ? false :true);
});

推荐答案

很好的问题，我编写了一些代码来使用数据属性检测未选中的选项.

Great question, i wrote some codes for detecting unselected options using data attributes.

$('#select').on('change', function() {  
    var selected = $(this).find('option:selected');
    var unselected = $(this).find('option:not(:selected)');
    selected.attr('data-selected', '1');
    $.each(unselected, function(index, value){
    	if($(this).attr('data-selected') == '1'){
      	    //this option was selected before
            alert("I was selected before " + $(this).val());
            $(this).attr('data-selected', '0');
        }
    });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select multiple id="select">
 <option data-selected=0 value="volvo">Volvo</option>
 <option data-selected=0 value="saab">Saab</option>
 <option data-selected=0 value="opel">Opel</option>
 <option data-selected=0 value="audi">Audi</option>
</select>

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