js不懂部分

1.js中apply和Math.max()函数的问题

function getMax(arr){
  return Math.max.apply(null, arr);
}

var arr=[1,3,6,3,7,9,2];
console.log(Math.max.apply(null,arr));

获取表格中td最大值

function getMax(arr){
  return Math.max.apply(null, arr);
}
function getTdMax(td){
    var arr=[];
    for(var i=0;i<td.length;i++){
     var ct=parseInt(td[i].innerHTML);
     arr.push(ct);
     }
     console.log(arr);
     var max=getMax(arr);
      console.log(max);
      for(var i=0;i<td.length;i++){
               if(td[i].innerHTML==max){
                   td[i].innerHTML='<i class="iconfont icon-huangguan"></i>'+max;
                   td[i].setAttribute('title','最大值');
               }
           }
}
function trMax(){
  getTdMax($("#contrastTable tr:eq(2) td:not(td:nth-child(1),td:nth-child(2))"));
  getTdMax($("#contrastTable tr:eq(3) td:not(td:nth-child(1),td:nth-child(2))"));
  getTdMax($("#contrastTable tr:eq(4) td:not(td:nth-child(1),td:nth-child(2))"));
  getTdMax($("#contrastTable tr:eq(6) td:not(td:nth-child(1),td:nth-child(2))"));
  getTdMax($("#contrastTable tr:eq(7) td:not(td:nth-child(1),td:nth-child(2))"));
}
trMax();