向对象数组Javascript中的对象添加元素

Question

问题很简单。我尝试了很多次，因此在stackoverflow中寻求帮助。 我有一个名为data的对象数组，它是从mongodb数据库返回的数据。 格式类似于：

 let data = [
{ booking: [ ref], max_booking: 0 },
{ booking: [ref], max_booking: 3 },
{ booking: [ref], max_booking: 5 },
{booking: [ref], max_booking: 4}
];

根据请求，我添加了来自数据库的真实数据：

[ { booking: [],
_id: null,
__v: 0,
comment: 'this is a comment',
date: 2020-07-26T00:00:00.000Z,
event_detail: 'this is event detail',
location: 'Kthm',
max_booking: 5,
meal_option: [ [Object] ],
sponsor_address: 'xxxx',
sponsor_name: 'yyyy',
id: null },
{ booking: [],
_id: 5ef60fab6c164281aee9ae2e,
date: 2020-07-30T00:00:00.000Z,
location: 'Kthm',
comment: 'this is another',
sponsor_name: 'Micorosft',
sponsor_address: 'USA',
event_detail: 'this is event detail',
meal_option: [ [Object] ],
max_booking: 5,
__v: 0,
id: '5ef60fab6c164281aee9ae2e' },
{ booking: [],
_id: 5ef6131f6c164281aee9ae30,
date: 2020-07-30T00:00:00.000Z,
location: 'TAN TOCK SENG HOSPITAL',
comment: 'this is dsadasdas',
sponsor_name: 'Asus',
sponsor_address: 'Los Angeles, USAssadsad',
event_detail: 'this is event detail',
meal_option: [ [Object] ],
max_booking: 5,
__v: 0,
id: '5ef6131f6c164281aee9ae30' },

]

我想执行如下操作： 当max_booking与任何对象上的预订数组的长度匹配时，应像该对象一样向该特定对象添加一个新元素。

{booking:[lets assume 5], max_booking: 5, result:1}

如果预订仍少于预定数量，则应添加一个新元素，但结果为0，如

{booking:[lets asssume 3], max_booking:5, result:0}

要执行此操作，我做了：

    data.map((d, i) => {
     if (d.booking.length === d.max_booking) {
      console.log("Fully Booked in index", i);
       d.result = 1;
     } else {
       console.log("Not booked");
       d.result = 0;
      }
      console.log(d.result);
    });
  console.log(data[3]);

现在让我们忽略其他应该小于符号。 foreach循环中d​​.result的值打印在控制台上，但是当我记录数据时，什么都没有改变。 谁能帮助我。预先感谢。

代码的屏幕截图：

输出屏幕截图：

Answer 1

为什么人们会放弃简单的for循环？

for(var i=0;i<data.length;i++) {
     if (data[i].booking.length === data[i].max_booking) {
       console.log("Fully Booked in index", i);
       data[i].result = 1;
     } else {
       console.log("Not booked");
       data[i].result = 0;
     }
}
console.log(data.result);

Answer 2

由于map（）return a new array，如果您更改map（）中的数据，则应像这样返回新数组：

var data = [{a:1},{a:2}]
data = data.map((d,i)=>{d.a = d.a+1; return d})

// Array [2]
// 0: Object { a: 2 }
​// 1: Object { a: 3 }
​

Answer 3

您似乎忘记了从地图内部返回d。您必须从map回调返回以获取新数组。

const data = [
  { booking: [], max_booking: 0 },
  { booking: [{}, {}, {}], max_booking: 3 },
  { booking: [], max_booking: 5 },
  { booking: [{}, {}, {}], max_booking: 4 },
]

const mapped = data.map((d, i) => {
  if (d.booking.length === d.max_booking) {
    console.log("Fully Booked in index", i);
    d.result = 1;
  } else {
    console.log("Not booked");
    d.result = 0;
  }
  console.log(d.result);
  return d
})

console.log(mapped)