How to set unique id in mongodb with JavaScript

Question

How to set unique id in mongodb with JavaScript

I have data like this

Mywants:[
    {"title":"lap","rate":$20}
    {"title":"lap","rate":$20}
    {"title":"lap","rate":$20}
]

If I save new data into array(mywant) I should save with new unique id so how to save like that using javascript. So it should be look like:

Mywants:[
    {"title":"lap","rate":$20,_id:objectId("512640f3243c837c0e0004401}
    {"title":"lap","rate":$20,_id:objectId("512640f3243c837254000001}
    {"title":"lap","rate":$20,_id:objectId("512640f3243c8372540257001}}
]

To insert I am using command like

collection.update({"userid":1248787885},{$push:{"Mywant":{"title":"car","rate":$100}}});

javascript
node.js
mongodb

Answer 1

As andyb notes, you have to generate the ObjectId for your new element by constructing a new one. But you don't need a separate library:

var mongodb = require('mongodb');
collection.update(
    {"userid":1248787885},
    {$push:{"Mywant":{
        _id: new mongodb.ObjectID(),
        "title":"car",
        "rate":$100
    }}});

Of course, $100 isn't a valid JavaScript type, but I assume you know that. It's also worth noting that Mongoose does this adding of _id fields to array elements for you, so that's another alternative.

Answer 2

To generate mongoDB ObjectId in JavaScript you can use an existing library or implement the BSON ObjectId specification yourself. ObjectId.js is one such library and getting an Id is as simple as:

var objectId = new ObjectId();

Answer 3

In javascript there is one method called Math.random() it will create dynamic random number so you can modify this number as dynamic id.