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this simple example builds REST API with following schema database of users

id:String, email: String ,gender:String, Name: String

The dependencies used in this project are as follows:

"dependencies": {
    "aws-sdk": "^2.1341.0",
    "dotenv": "^16.0.3",
    "express": "^4.18.2",
    "nodemon": "^2.0.22"
  }

We will create a .env file and store all the Credential needed to connect and communicate with the AWS-DynamoDB. it should look as such

AWS_ACCESS_KEY_ID=BHFAWHJBJHVSES
AWS_SECRET_ACCESS_KEY=MNGk9KBjjhkjDGHVbjbhjDFGCFDS
AWS_DEFAULT_REGION=us-west-1

We will set up the configuration for DynamoDB in the file DynamoDB.js

Then we will create the CRUD function to create , read, update and delete user info from dynamodb.

Below is the code for dynamodb.js

import AWS from 'aws-sdk';
import dotenv from 'dotenv';

// here we are loading the environment variables from the .env file
dotenv.config();
// here we are destructuring the AWS object to get the config and DynamoDB object
const{config, DynamoDB} = AWS;

// here we are configuring the AWS environment
AWS.config.update({
    region: process.env.AWS_DEFAULT_REGION,
    accessKeyId: process.env.AWS_ACCESS_KEY_ID,
    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
    maxRetries:10,
    retryDelayOptions: {base: 200}
})

// here we are creating a new instance of the DynamoDB client
export const dynamoClient = new DynamoDB.DocumentClient();

// this is the name of the table we created in DynamoDB
const TABLE_NAME = "users";

// this is the function that will get all the users from the table, it will return a promise
export const getUsers = async ()=>{
    const params = {
        TableName:TABLE_NAME
    };
    return await dynamoClient.scan(params).promise();
}

// this is the function that will get a user by id(individual entry), it will return a promise
export const getUserByID = async (id)=>{
    const params = {
        TableName: TABLE_NAME,
        Key:{
            id
        }
    }
    return await dynamoClient.get(params).promise();
}

// this is the function that will add or update a user(if the entry already exist with the same id will update), it will return a promise
export const AddorUpdateUser = async (user)=>{
    const params ={
        TableName: TABLE_NAME,
        Item: user
    }
    return await dynamoClient.put(params).promise();
}

// this is the function that will delete a user by id, it will return a promise
export const deleteUser = async(id)=>{
    const params ={
        TableName: TABLE_NAME,
        Key:{
            id
        }
    }
    return await dynamoClient.delete(params).promise();
}

All the routing for different operations , getAllUsers, GetUserById, EditUser & Delete User will be setup in a separate file called index.js.

We will setup a initial home route that will display some message when the server is loaded and running.

we will be using. a middleware that will return our entry in json format

we will be creating 5 separate routes to carry out the CRUD functions via REST API

we will tell set a port where our server will run and listen for any user inputs

Below is the full code covering all these concepts , in index.js file

import express from 'express';
import {getUsers, getUserByID,deleteUser, AddorUpdateUser} from './/dynamodb.js';

const app = express();

// here we are telling express to use the json middleware
app.use(express.json());

// this is the route that will be called when we go to the root of the server; a home page-route
app.get('/',(req,res)=>{
    res.send('Welcome to Local Server. Get ready to be amazed')
})

// this is the route that will get all the users from the table
// we are using async/await to handle the promises
// we are using try/catch to handle the errors
app.get('/users', async (req,res)=>{
    try {
        const users = await getUsers();
        res.json(users);
    } catch (error) {
        console.log(error);
        res.status(500).json({error:error.message})  
    }
})

// this is the route that will get a user by id. need to pass the id as a parameter
app.get('/users/:id', async (req,res)=>{
    try {
        const users = await getUserByID(req.params.id);
        res.json(users);
    } catch (error) {
        console.log(error);
        res.status(500).json({error:error.message})  
    }
})

// this is the route that will add or update a user
app.post('/users', async(req,res)=>{
    const user = req.body;
    try {
        const newUser = await AddorUpdateUser(user);
        res.json(newUser)
    } catch (error) {
        console.log(error);
        res.status(500).json({error:error.message})  
        
    }
})

// this is the route that will edit an existing user. need to pass the id as a parameter
app.put('/users/:id',async(req,res)=>{
    const user = req.body;
    const {id} = req.params;
    user.id = id;
    try {
        const newUser = await AddorUpdateUser(user);
        res.json(newUser)
    } catch (error) {
        console.log(error);
        res.status(500).json({error:error.message})
        
    }
})

// this is the route that will delete a user
app.delete('/users/:id', async(req,res)=>{

    try {
        const user = await deleteUser(req.params.id);
        res.json(user)
    } catch (error) {
        console.log(error);
        res.status(500).json({error:err})
        
    }
})

// this is the port that the server will listen to
// we are using the environment variable PORT if it is available, if not we are using 8080
const port = process.env.PORT || 8080;

// here we are telling the server to listen to the port
app.listen(port,()=>{
    console.log(`Server is running on port ${port}`)
})

Below is the snapshot of GetAllUsers returned in our server

{
"Items": [
{
"email": "bellawati@gmail.com",
"id": "2",
"name": "Bella koirala",
"gender": "female"
},
{
"email": "test@email.com",
"id": "1",
"name": "testing tester",
"gender": "male"
}
],
"Count": 2,
"ScannedCount": 2
}

Happy Coding !