js控制單選複選框（全選)

//獲取單選按鈕的選項值         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="反選" /><br />     <input id="childChk1" type="checkbox" value="cf"/>吃飯<br/>     <input id="Checkbox2" type="checkbox" value="sj"/>睡覺<br/>     <input id="Checkbox3" type="checkbox" value="dq"/>打球<br/> //複選框的全選功能 function checkAll() {             //觸發事件對象，全選的checkbox             var obj = event.srcElement;             //全部的input標籤             var inputs = document.getElementsByTagName("input");             for (var i = 0; i < inputs.length; i++) {                 //判斷當前的對象是否是input對象，是否是checkbox                 if (inputs[i].type == "checkbox") {                     inputs[i].checked = obj.checked;                 }             }         } //給全部的 子checkbox註冊事件，若是全部的子checkbox都打勾了，則全選也打勾         window.onload = function () {             var inputs = document.getElementsByTagName("input");             for (var i = 0; i < inputs.length; i++) {                 if (inputs[i].type == "checkbox") {                     //去掉全選的那個chexkbox                     if (inputs[i].id != "chkAll") {                         //給每一個子checkbox註冊事件                         inputs[i].onclick = function () {                             //判斷子checkbox是否是被選中了                             //假設全部的都被選中                             var isCheckAll = true;                             for (var j = 0; j < inputs.length; j++) {                                 if (inputs[j].type == "checkbox" && inputs[j].id != "chkAll") {                                     //判斷子的checkbox是否被選中                                     if (!inputs[j].checked) {                                         isCheckAll = false;                                         break;                                     }                                 }                             }                             //設置全選狀態                             document.getElementById("chkAll").checked = isCheckAll;                         }                     }                 }             }         }