db.mongo.insert({name:'mongo'});
> var t=db.mongo.findOne();
> t
{ "_id" : ObjectId("5141b98723616e67f947f356"), "name" : "mongo" }
> var d=t
> d
{ "_id" : ObjectId("5141b98723616e67f947f356"), "name" : "mongo" }
> d.password=123
123
> d
{
"_id" : ObjectId("5141b98723616e67f947f356"),
"name" : "mongo",
"password" : 123
}
> t
{
"_id" : ObjectId("5141b98723616e67f947f356"),
"name" : "mongo",
"password" : 123
}
问题1
var d = t
是引用赋值吗 如果是的话，怎么样不使用引用赋值
delete d.password
true
> d
{ "_id" : ObjectId("5141b98723616e67f947f356"), "name" : "mongo" }
> d.password=124
124
> d
{
"_id" : ObjectId("5141b98723616e67f947f356"),
"name" : "mongo",
"password" : 124,
"password" : 124
}
问题2 我执行
delete d.password
返回 true 说明已经删除，为什么我再执行
d.password=124
会执行两次添加
> d
{
"_id" : ObjectId("5141b98723616e67f947f356"),
"name" : "mongo",
"password" : 124,
"password" : 124
}
刚开始接触 不是很明白，希望有知道的说明下原因
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
The first question... Because the two entries have the same
ObjectId, they are regarded as the same one...Although it is not actually a reference assignment, you can understand it this way...
The second problem cannot be reproduced, so I don’t know...
This is either the same problem with ObjectId, or simply JavaScript syntax requires reference assignment. If you want to clone, watch this. http://stackoverflow.com/questions/122102/most-efficient-way-to-clone-an-object
I haven’t encountered the second problem either.
Yes, this is purely a Javascript syntax issue. This problem exists in Javascript. That is, the problem of deep copy and shallow copy:
Code transferred from https://www.zhihu.com/question/23031215