javascript - 获取更改的旧单选按钮

Question

我的页面中有一组单选按钮。在更改时，我想知道哪个按钮未被选中，但onchange事件$(this)指的是新选择的按钮，有没有办法让旧的未选中按钮？

  window.old = null;
  $('.radio').change(function(){ 
  alert($(this).val()); // this is the selected
  alert($(window.old).val()); // this is the old one
  })

Answer 1

只需将最后点击的收音机保存到变量中，

window.old = null;

$(document).ready(function() {
    window.old = $('.radio:checked');
});

$('.radio').change(function() {
    alert($(this).html());

    if (window.old) {
        alert($(window.old).html());
    }

    window.old = this;
})

Answer 2

保存单击时的单选按钮（更改前），并在新的单击时读取单选按钮，代码如下：

window.old = null;
$('.radio').click(function () {
    // Store the current radio on click, before it changes
    window.old = this;
}).change(function() {
    // Do something with the old radio value after the change
    console.log('previous radio:', window.old);
});​

查看演示http://jsfiddle.net/JL8V2/

Answer 3

没有全局变量

$('input[type="radio"]').click(
    function (e)
    {
        var me = $(this);
        var grp = $("input[type='radio'][name='" + me.attr('name') + "']");
        if (me.val() === me.data('last-val'))
        {
            me.prop('checked', false);
            grp.data('last-val', null);
        }
        else
        {
            grp.data('last-val', me.val());
        }
    }
);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

<fieldset >
    <legend> Group 1 </legend>
    <label>
    <input type="radio" name='grp1' value='1'/>
        You can select me
    </label>
    <label>
    <input type="radio" name='grp1' value='2'/>
        But you can
        </label>
    <label>
    <input type="radio" name='grp1' value='3'/>
        Change your idea either
        </label>
</fieldset>

<fieldset >
    <legend> Group 2 </legend>
    <label>
    <input type="radio" name='grp2' value='1'/>
        Just give another click
    </label>
    <label>
    <input type="radio" name='grp2' value='2'/>
        But remember, for this work
        </label>
    <label>
    <input type="radio" name='grp2' value='3'/>
        Values must be unique in each group
        </label>
</fieldset>