Javascript 如何获取两个数组对象之间的差异项？

这里我有两个数组，但它们不是简单的数组。请参见以下内容：

var a = [{"id":1,"in":1,"num":3000},{"id":2,"in":1,"num":1500},{"id":3,"in":1,"num":1000}]
var b = [{"id":1,"in":0,"num":1000},{"id":2,"in":0,"num":1000}]

for (var i = a.length - 1; i >= 0; i--) {
     for (var j =b.length - 1; j >= 0; j--) {
        if( a[i]['id'] == b[j]['id']){
             a[i]['rest'] = a[i]['num'] - b[j]['num']
         }
      }
 }
 console.log(a)

但我无法获取id 3，因为id 3不在b数组中。请帮忙

这是我想要的答案

a = [
   {"id":1,"in":1,"num":3000,"rest":2000},
   {"id":2,"in":1,"num":1500,"rest":500},
   {"id":3,"in":1,"num":1000,"rest":1000}
]

---

thk

那么，对于a的每个元素，您想从a中相应的“num”中减去b中的“num”？而不仅仅是迭代a并检查它是否也包含在b中：

var a = [{"id":1,"in":1,"num":3000},{"id":2,"in":1,"num":1500},{"id":3,"in":1,"num":1000}]
var b = [{"id":1,"in":0,"num":1000},{"id":2,"in":0,"num":1000}]

for (var i = a.length - 1; i >= 0; i--) {
  a[i]['rest'] = a[i]['num'];
  for (var j =b.length - 1; j >= 0; j--) {
    if( a[i]['id'] == b[j]['id']){
     a[i]['rest'] = a[i]['num'] - b[j]['num'];
     break;
    }
  }
}

---

您可以为

标志添加一些变量，以了解您是否拥有相同的
id
，下面是一个代码示例

var flag;
var a = [{"id":1,"in":1,"num":3000},{"id":2,"in":1,"num":1500},{"id":3,"in":1,"num":1000}]
var b = [{"id":1,"in":0,"num":1000},{"id":2,"in":0,"num":1000}]

for (var i = a.length - 1; i >= 0; i--)
    flag = false;
    for (var j =b.length - 1; j >= 0; j--) {
        if( a[i]['id'] == b[j]['id']){
            a[i]['rest'] = a[i]['num'] - b[j]['num']
            flag = true;
        }
    }
    if(!flag) {
        a[i]['rest'] = a[i]['num']
    }
}

@AbdulJabbar如果项不在b数组中。只使用a的值。有什么问题吗？你能重新表述你的问题吗？就目前而言，这毫无意义：/你应该从['id'中得到什么？它不正确：（只需添加
中断
，我想30mins@RyanYiada对不起，你什么意思？