How to add unique constraint in collection of MongoDB using Node.js?

Last Updated : 08 Feb, 2021

Mongoose module is one of the most powerful external modules of the node.js.Mongoose is a MongoDB ODM i.e (Object database Modelling) that used to translate the code and its representation from MongoDB to the Node.js server. Mongoose module provides several functions in order to manipulate the documents of the collection of the MongoDB database.

Unique constraint: We can add a unique constraint on the value of the document collection in MongoDB so that all the documents can be distinguished easily. A unique constraint is added during the creation of the structure of the collection in Node.js

Installing Module:

npm install mongoose

Project Structure:

Running the server on Local IP: Data is the directory where the MongoDB server is present.

mongod --dbpath=data --bind_ip 127.0.0.1

Filename- index.js:

JavaScript

// Importing mongoose module
const mongoose = require("mongoose");

// Database Address
const url = "mongodb://localhost:27017/GFG";

// Connecting to database
mongoose
  .connect(url)
  .then((ans) => {
    console.log("ConnectedSuccessful");
  })
  .catch((err) => {
    console.log("Error in the Connection");
  });
  
// Calling Schema class
const Schema = mongoose.Schema;

// Creating Structure of the collection
const collection_structure = new Schema({
  name: {
    type: String,
    require: true,
  },
  marks: {
    type: Number,
    default: 0,
  },
});

// Creating collection
const collections = 
    mongoose.model("GFG2", collection_structure);

// Inserting one document
collections
  .create({
    name: "aayush",
  })
  .then((ans) => {
    console.log("Document inserted");
    
    // Inserting invalid document
    collections
      .create({
        name: "saini",
        marks: "#234",
        phone: 981,
      })
      .then((ans) => {
        console.log(ans);
      })
      .catch((err) => {
      
        // Printing the documents
        collections.find().then((ans) => {
          console.log(ans);
        });
        
        // Printing the Error Message
        console.log(err.message);
      });
  })
  .catch((err) => {
  
    // Printing Error Message
    console.log(err.message);
  });