In the previous post, I talk about what MongoDB is, what are the basic API. In this post, I am going to share some more details about the API to do CRUD operation (Create, Read, Update, Delete), and introduction to mongoose.js.

source

What Will I Learn?

• CRUD Operation with Mongo Console
• Introduction to mongoose (with MVC method)

Requirements

• MongoDB installed, and mongo shell start running
• Node.js installed
• NPM installed
• Understand JavaScript and basic MVC methadology

Difficulty

Intermediate

Tutorial Contents

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Before reading through the tutorial, you need to setup mongodb and make sure mongodb is running.

Write Database Query with JavaScript

Some cool thing you can do with MongoDB is that you can write the Mongo Command in JavaScript and load it in the mongo console.

The reason is that MongoDB was build with C, C++ and JavaScript. So, JavaScript can be used to make query in MongoDB.

Example:
create these js files.

• userInfo1.js

db.users.insert({
    name: {
        firstName: "Johnson",
        lastName: "Lai"
    },
    age: 22,
    skills: ["javascript", "sql", "electronics"]
    });
db.users.insert({
    name: {
        firstName: "Johnson 2",
        lastName: "Lai 2"
    },
    age: 10,
    skills: ["javascript", "sql", "machine learning", "electronics"]
    });

• userInfo2.js

var userArr = [
{
    name: {
        firstName: "Johnson",
        lastName: "Lai"
    },
    age: 22,
    skills: ["javascript", "sql", "electronics"]
},
{
    name: {
        firstName: "Johnson 2",
        lastName: "Lai 2"
    },
    age: 10,
    skills: ["javascript", "sql", "machine learning", "electronics"]
    }
];
db.users.insert(userArr);

Both userInfo1.js and userInfo2.js can be loaded in mongo console.

In Mongo Console:

• Change to a database with use usersInfo;

• Then, load that file with load("c:/testfile/usersInfo1.js");, the console should return true to indicate that the file is loaded.

• The data will be inserted into database. To check it simply run db.users.find().pretty()

CRUD Operation with MongoDB

Create

db.users.insert({name: "superoo7"});

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### Read #### Get all data ``` db.users.find().pretty(); ```

Get data that match the specific value (Equal, $eq)

db.users.find({"name.firstName": "Johnson"}).pretty();
db.users.find({"age": {$eq:10}}).pretty();

$eq in the command in mongo context means equal.

Get data with comparing data (Greater Than, $gt or Less Than, $lt)

db.users.find({"age": {$gt:9}}).pretty();

This query with $gt are finding data with an age greater than 9.

Other operator

Greater than or equal ($gte)

db.users.find({"age": {$gte:10}}).pretty();

Less than or equal ($lte)

db.users.find({"age": {$lte:10}}).pretty();

Not Equal ($ne)

db.users.find({"age": {$ne:10}}).pretty();

In ($in)

Find value in an array, to check the existance of that value.

db.users.find({"skills": {$in: ["javascript"]}}).pretty();

Not in ($nin)

Return the value that are not in the array.

db.users.find({"skills": {$in: ["micro economy"]}}).pretty();

Exist

Return the value that exists

db.users.find({"skills": {$exists: true}}).pretty();

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Update

For update operation, it takes in 2 objects, which is: the search object, and the update object. The query looks like this: db.users.update(<search term>, <update term>)

Update a data

db.users.update(
    {"name.firstName": "Johnson"}, {$set: {"name.lastName": "Lai WH"} } );

Upsert

If the data does not exist, instead of update, it will create new one.

db.users.update(
    {"name.firstName": "Johnny"}, {$set: {"name.lastName": "Depp"} }, {upsert: true} );

Update an array

Using $set is important. Without it, the data will not update.

db.users.update(
    {"name.firstName": "Johnson"}, {$set: {"skills.1": "HTML"} } );

This query will make ["javascript", "sql", "electronics"] into ["javascript", "HTML", "electronics"]

Delete

Delete all that match

db.users.remove({"name.firstName": "Johnson"});

Delete One

db.users.remove({"name.firstName": "Johnson"}, 1);

Delete All

db.users.remove({});

Mongoose

Mongoose.js is a schema based solution to model your data in mongoDB. The schema creates key value pair for your data type

Get started

With Mongoose, Model-View-Controller can be practice.

The file structure can look like:

Folder
|- index.js
|- controller/
    |- book.js
|- model/
    |- book.js 

Connect to the database with this method in the main index.js file.

const mongoose = require('mongoose');
let dbLink = 'mongodb://localhost/dbName'
mongoose.connect(dbLink);

Create a schema to state how the data looks like.

In the model/book.js file

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
let bookSchema = new Schema({
        title: String,
        keywords: Array,
        published: Boolean
    });
module.exports = mongoose.model('Book', bookSchema);

In the controller/book.js file

const mongoose = require('mongoose');
const Book = require('../model/book');
let displayBook = () => {
    // Find all book
    Book.find({}, (err, books) => {
        if(err) {
            throw 'ERROR';
        }
        return;
    }).then(data => {
        console.log(data);
    }).catch(err => console.log(err))
};
module.exports = displayBook;

in main file index.js, simply just call the controller to get the data.

let displayBook = require('./controller/book');
displayBook();

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Curriculum

• Getting started with MongoDB ( steemit | utopian)

That is all for me in this blog post. In the upcoming blog post, I will share some operation with mongoose, and making mongodb into production.

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Posted on Utopian.io - Rewarding Open Source Contributors

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