js全选反选

<!DOCTYPE html>
<html>
   <head>
       <meta charset="UTF-8">
       <title></title>
   </head>
   <body>
       <form action="" method="post" >
           <input type="checkbox" name="" class="aa" value="" />冬哥<br />
           <input type="checkbox" name="" class="aa" value="" />冬爷<br />
           <input type="checkbox" name="" class="aa" value="" />冬少<br />
           <input type="checkbox" name="" class="aa" value="" />冬王<br />
           <input type="checkbox" name="" class="aa" value="" />冬雪<br />
           <input type="checkbox" name="" class="aa" value="" />冬天<br />
           <input type="button" οnclick="quanxuan()" value="全选"/><br />
           <input type="button" οnclick="fanxuan()" value="反选"/>
       </form>
       <script type="text/javascript">
           let aa= document.getElementsByClassName('aa');
           function quanxuan() {
               let a = aa.length;
               let b = 0;
               for (let i = 0; i < a; i++) {
                  if (aa[i].checked =="") {
                      aa[i].checked = true;
                  } else{
                      b++;
                  }
               }
               if(b == a){
for(let i = 0; i < a; i++){
   aa[i].checked=false;

   }
   }
           }
           function fanxuan() {
               let a= aa.length;
               for (let i = 0; i < a; i++) {
                  if (aa[i].checked == '') {
                      aa[i].checked = true;
                  } else{
                      aa[i].checked = false;
                  }
               }
           }
       </script>
   </body>
</html>

js全选反选

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