单选按钮的OnChange事件处理程序（INPUT type =“ radio”）不能用作一个值

var rad = document.myForm.myRadios;var prev = null;for (var i = 0; i < rad.length; i++) {    rad[i].addEventListener('change', function() {        (prev) ? console.log(prev.value): null;        if (this !== prev) { prev = this;        }        console.log(this.value)    });}<form name="myForm">  <input type="radio" name="myRadios"  value="1" />  <input type="radio" name="myRadios"  value="2" /></form>

这是一个JSFiddle演示：https
://jsfiddle.net/crp6em1z/