js控制单选复选框（全选)

//获取单选按钮的选项值         function f1() {             //radio集合             var radios = document.getElementsByName("sex");             for (var i = 0; i < radios.length; i++) {                 if (radios[i].checked) {                     alert(radios[i].value);                     break;                 }             }         }     <input type="checkbox" id="chkAll" id="btn" type="button" value="反选" /><br />     <input id="childChk1" type="checkbox" value="cf"/>吃饭<br/>     <input id="Checkbox2" type="checkbox" value="sj"/>睡觉<br/>     <input id="Checkbox3" type="checkbox" value="dq"/>打球<br/> //复选框的全选功能 function checkAll() {             //触发事件对象，全选的checkbox             var obj = event.srcElement;             //全部的input标签             var inputs = document.getElementsByTagName("input");             for (var i = 0; i < inputs.length; i++) {                 //判断当前的对象是否是input对象，是否是checkbox                 if (inputs[i].type == "checkbox") {                     inputs[i].checked = obj.checked;                 }             }         } //给全部的 子checkbox注册事件，若是全部的子checkbox都打勾了，则全选也打勾         window.onload = function () {             var inputs = document.getElementsByTagName("input");             for (var i = 0; i < inputs.length; i++) {                 if (inputs[i].type == "checkbox") {                     //去掉全选的那个chexkbox                     if (inputs[i].id != "chkAll") {                         //给每一个子checkbox注册事件                         inputs[i].onclick = function () {                             //判断子checkbox是否是被选中了                             //假设全部的都被选中                             var isCheckAll = true;                             for (var j = 0; j < inputs.length; j++) {                                 if (inputs[j].type == "checkbox" && inputs[j].id != "chkAll") {                                     //判断子的checkbox是否被选中                                     if (!inputs[j].checked) {                                         isCheckAll = false;                                         break;                                     }                                 }                             }                             //设置全选状态                             document.getElementById("chkAll").checked = isCheckAll;                         }                     }                 }             }         }