问如何利用JavaScript计算数值的总和？

$("#timediff").on("keyup", function() {

    var v_id = Number("0"); 

    $("input:checked").each(function () { 

      v_id = Number(v_id) +Number($("input:checked").val());

    alert(v_id);

    });

    var s_id = $("#timediff").val();

    if (s_id<=v_id) {

       alert('The"' + s_id +' h" are smaller than "' + v_id + 'h"');

    }else{

          alert('The"' + s_id +' h" are bigger than "' + v_id + 'h"');

    }

  });