来自onclick的sum值获取请求foreachjquery

您必须total在click事件处理程序之外初始化变量.

var total = 0;
$(".checks").on("click", function(){
  var clicked = $(this);
  var room = clicked.val();

  $.get('/rooms.json', function(data){ 
    data.forEach(function(d){
      if(room == d.id){
        total += parseInt(d.room_type.price);
        $("#selected_rooms").append("
" + d.number + " @ " + d.room_type.price + "
");
        $("#total_amount").html("
" + total + "
");
      }
    });
  });
});