Yes there is no change event for currently selected radio button. But problem is when each radio button is taken as a separate element. Instead a radio group should be considered a single element like select. So change event is triggered for that group. If it is a select element we never worry about each option in it, but take only the selected option. We store the current value in a variable which will become the previous value, when a new option is selected. Similarly you have to use a separate variable for storing value of checked radio button.

如果您想要识别前一个单选按钮，则必须循环鼠标按下事件。

var radios = document.getElementsByName("myRadios");
var val;
for(var i = 0; i < radios.length; i++){
    if(radios[i].checked){
        val = radios[i].value;
    }
}

请看这个:http://jsfiddle.net/diode/tywx6/2/

如何使用Jquery的变化事件?

$(function() {
    $('input:radio[name="myRadios"]').change(function() {
        if ($(this).val() == '1') {
            alert("You selected the first option and deselected the second one");
        } else {
            alert("You selected the second option and deselected the first one");
        }
    });
});

jsfiddle: http://jsfiddle.net/f8233x20/

最简单和动力十足

使用getAttribute只读无线电输入

文件。addEventListener“输入”,(e) = > { 如果目标(e。“name”getAttribute () = = myRadios”) 控制台日志(e .目标。价值) }) <输入类型=“无线电 <输入类型=“无线电

您可以添加以下JS脚本

<script>
    function myfunction(event) {
        alert('Checked radio with ID = ' + event.target.id);
    }
    document.querySelectorAll("input[name='myRadios']").forEach((input) => {
        input.addEventListener('change', myfunction);
    });
</script>

除了存储之前的状态，我不认为还有其他方法。 下面是使用jQuery的解决方案

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> 
<script type="text/javascript">
    var lastSelected;
    $(function () {
        //if you have any radio selected by default
        lastSelected = $('[name="myRadios"]:checked').val();
    });
    $(document).on('click', '[name="myRadios"]', function () {
        if (lastSelected != $(this).val() && typeof lastSelected != "undefined") {
            alert("radio box with value " + $('[name="myRadios"][value="' + lastSelected + '"]').val() + " was deselected");
        }
        lastSelected = $(this).val();
    });
</script>

<input type="radio" name="myRadios" value="1" />
<input type="radio" name="myRadios" value="2" />
<input type="radio" name="myRadios" value="3" />
<input type="radio" name="myRadios" value="4" />
<input type="radio" name="myRadios" value="5" />

在考虑了一会儿之后，我决定去掉变量并添加/删除类。这是我得到的:http://jsfiddle.net/BeQh3/2/

如图所示: http://www.w3schools.com/jsref/event_onchange.asp 单选按钮不支持onchange属性。

您链接的第一个SO问题给出了答案:使用onclick事件，并检查它触发的函数内部的单选按钮状态。