blocks|key|514723|text|ObjectID是对象，所以如果只将它们与==进行比较，就是在比较它们的引用。如果要比较它们的值，则需要使用ObjectID.equals方法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|514724|if+(results.userId.equals(AnotherMongoDocument._id))+{
++++...
}|code-block|syntax|javascript|514725|entityMap^0|0|8|L|2|1I|F|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|L|$]]

<code>ObjectID</code>s are objects so if you just compare them with <code>==</code> you're comparing their references. If you want to compare their values you need to use the <code>ObjectID.equals</code> method:

<pre><code>if (results.userId.equals(AnotherMongoDocument._id)) {
 ...
}
</code></pre>

blocks|key|514778|text|Mongoose使用mongodb本地驱动程序，该驱动程序使用自定义的ObjectID类型。可以将ObjectID与.equals()方法进行比较。以results.userId.equals(AnotherMongoDocument._id)为例。如果您希望以ObjectID格式存储ObjectID的字符串化版本或cookie，则JSON类型还有一个toString()方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|514779|如果您使用ObjectID+=+require("mongodb").ObjectID+(需要mongodb原生库)，您可以使用results.userId+instanceof+ObjectID检查results.userId是否是有效的标识符。|514780|等。|514781|entityMap^0|1M|9|23|1B|4X|A|0|5|12|1S|Y|2S|E|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|K|$]]

Mongoose uses the mongodb-native driver, which uses the custom ObjectID type. You can compare ObjectIDs with the <code>.equals()</code> method. With your example, <code>results.userId.equals(AnotherMongoDocument._id)</code>. The ObjectID type also has a <code>toString()</code> method, if you wish to store a stringified version of the ObjectID in JSON format, or a cookie.

If you use <code>ObjectID = require("mongodb").ObjectID</code> (requires the mongodb-native library) you can check if <code>results.userId</code> is a valid identifier with <code>results.userId instanceof ObjectID</code>.

Etc.

blocks|key|514856|text|被接受的答案确实限制了你可以用你的代码做什么。例如，您不能使用Object+Ids方法搜索equals数组。相反，总是转换为字符串并比较键会更有意义。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|514857|如果您需要使用indexOf()在引用数组中检查特定id，这里有一个示例答案。假设query是您正在执行的查询，假设someModel是您正在查找的id的mongo模型，最后假设results.idList是您要在其中查找对象id的字段。|514858|query.exec(function(err,results){
+++var+array+=+results.idList.map(function(v){+return+v.toString();+});
+++var+exists+=+array.indexOf(someModel._id.toString())+>=+0;
+++console.log(exists);
});|code-block|syntax|javascript|514859|entityMap^0|V|A|0|7|9|15|5|1M|9|2H|E|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|N|$]]

The accepted answers really limit what you can do with your code. For example, you would not be able to search an array of <code>Object Ids</code> by using the equals method. Instead, it would make more sense to always cast to string and compare the keys. 

Here's an example answer in case if you need to use <code>indexOf()</code> to check within an array of references for a specific id. assume <code>query</code> is a query you are executing, assume <code>someModel</code> is a mongo model for the id you are looking for, and finally assume <code>results.idList</code> is the field you are looking for your object id in.

<pre><code>query.exec(function(err,results){
 var array = results.idList.map(function(v){ return v.toString(); });
 var exists = array.indexOf(someModel._id.toString()) &gt;= 0;
 console.log(exists);
});
</code></pre>

blocks|key|298258|text|将对象id转换为字符串(使用toString()方法)就可以了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|298259|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

converting object id to string(using toString() method) will do the job.

blocks|key|298315|text|我遇到了完全相同的问题，在JSON.stringify()的帮助下我简单地解决了这个问题，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|298316|if+(JSON.stringify(results.userId)+===+JSON.stringify(AnotherMongoDocument._id))+{
++++++++console.log('This+is+never+true');
}|code-block|syntax|javascript|298317|entityMap^0|D|G|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

I faced exactly the same problem and i simply resolved the issue with the help of <code>JSON.stringify()</code> as follow:- 

<pre><code>if (JSON.stringify(results.userId) === JSON.stringify(AnotherMongoDocument._id)) {
 console.log('This is never true');
}
</code></pre>

I have a node.js application that pulls some data and sticks it into an object, like this:

<pre><code>var results = new Object();

User.findOne(query, function(err, u) {
 results.userId = u._id;
}
</code></pre>

When I do an if/then based on that stored ID, the comparison is never true:

<pre><code>if (results.userId == AnotherMongoDocument._id) {
 console.log('This is never true');
}
</code></pre>

When I do a console.log of the two id's, they match exactly:

<pre><code>User id: 4fc67871349bb7bf6a000002 AnotherMongoDocument id: 4fc67871349bb7bf6a000002
</code></pre>

I am assuming this is some kind of datatype problem, but I'm not sure how to convert results.userId to a datatype that will result in the above comparison being true and my outsourced brain (aka Google) has been unable to help.

Comparing mongoose _id and strings

JSON

我有一个node.js应用程序，它提取一些数据并将其放入一个对象中，如下所示：var results = new Object();User.findOne(query, function(err, u) {    results.userId = u._id;}当我根据存储的ID执行if/then时，比较结果永远不会...

问比较mongoose _id和字符串
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