获取input值自动求和

function sum() {
var airTicket=Number($("input[ name='airTicket' ] ").val());
var transportationFee=Number($("input[ name='transportationFee' ] ").val());
var trainFare=Number($("input[ name='trainFare' ] ").val());
var hotelExpense=Number($("input[ name='hotelExpense' ] ").val());
var mealFee=Number($("input[ name='mealFee' ] ").val());
var baseFee=Number($("input[ name='baseFee' ] ").val());
$("input[ name='total' ]").attr("value",airTicket+transportationFee+trainFare
+hotelExpense+mealFee+baseFee);

}