js正则、js全选、反选、全不选、ajax批删

<button onclick="fun1()">全选</button>
<button onclick="fun2()">全不选</button>
<button onclick="fun3()">反选</button>
<button onclick="fun4()">批量删除</button>
<input type="checkbox" id="a" onclick="fun()"/>全选全不选

<script>
var box=document.getElementsByName("box");
function fun1(){
    for(i=0;i<box.length;i++){
         box[i].checked=true;
    }
}
  function fun2(){
      for(i=0;i<box.length;i++){
          box[i].checked=false;
      }
  }
  function fun3(){
      for(i=0;i<box.length;i++) {
          if (box[i].checked) {
              box[i].checked = false;
          } else {
              box[i].checked = true;
          }
      }
  }
  //全选全不选
  function fun(){
      var a=document.getElementById("a");
      for(i=0;i<box.length;i++){
          if (a.checked==true) {
              box[i].checked = true;
          } else {
              box[i].checked = false;
          }
      }
  }
//批量删除
function fun4(){
    for(i=box.length-1;i>=0;i--){
        if(box[i].checked==true){
            var  ajax1=new XMLHttpRequest();
            ajax1.onreadystatechange=function(){
                if(ajax1.readyState==4 && ajax1.status==200){
                    var bb=ajax1.responseText;
                    if(ajax1.responseText){
                        box[i].parentNode.parentNode.remove();
                        alert("删除成功");
                    }else{
                        alert("删除失败");
                    }
                }
            }
            ajax1.open('get','__URL__/shan/id/'+box[i].value,false);
            ajax1.send();
        }
    }
</script>