Node JS Tutorial

What is Node JS?

Node JS is an open source and cross-platform JavaScript Runtime to run JavaScript outside web browser. Node JS is used to build scalable web/window/console application, Web APIs and Hybrid applications. It is build on Chrome's V8 engine.

Node JS is asynchronous and event-driven JavaScript runtime build for scalable network applications. Although JavaScript in web browser is single thread and synchronous, Node JS is asynchronous and can use multi threads for I/O or others tasks in background.

JavaScript was meant for web browser only, but using Node JS, we can use JavaScript outside web browser to build scalable applications.

Node JS Timeline

Node JS Applications

Node JS is based on Chrome's V8 engine, one of the fastest JavaScript engine. Node JS use asynchronous event-driven runtime. Node JS can handle many concurrent connection at one time.

The JavaScript Execution in Node JS is single thread and Non Blocking making Node JS one of the Fastest Backend Server that can handle many concurrent at time with low RAM and best use of CPU.

Node JS Performance Secret

JavaScript is Single Thread for execution of code in a web browser. For long operations like Timers, Ajax, Fetch, Promises, JavaScript use Async callback functions. The same way Node JS works, but by using asynchronous and event driven architecture. Using this technique, Node JS can handle much more connections than Apache Web Server with very low memory.

Apache can handle upto 10k connection. But Node JS can handle more then double connections at one time.

With Callback

console.log(1);
    
setTimeout(()=>{ console.log(2)});  // will run after 3
    
console.log(3);
    

With Promise Callback

console.log(1);
    
const p = Promise.resolve(2);
p.then(i=>console.log(i));  // will run after 3
    
console.log(3);
    

With Promise Callback

console.log(1);
    
setTimeout(()=>{ console.log(2)});
const p = Promise.resolve(3);
p.then(i=>console.log(i));  
    
console.log(4);
    

As we can see that there is a callback function in setTimeout function, thus JavaScript will not block here and execute third line first. After main thread is free (after printing 3), now callback function in timer will be executed by Event Loop and we will get 2.

In the same manner, file handling and database connections are handled in Node JS. By using Non Blocking approach for long waiting tasks, Node JS can handle multiple connections using a single thread.

Blocking Request in NodeJS

const fs = require('fs');
const data = fs.readFileSync('/data.txt');
console.log(data);           
console.log("done");     // will run after data      
    

Non Blocking Request in NodeJS

const fs = require('fs');
const data = fs.readFile('/data.txt',(err,output)=>{
    if(err){
        console.warn("error");
    }
    else{
        console.log(output);
    }
});       
console.log("app running");      // will run first     
    

Event Loop

As javascript is single thread, it use event loop to handle asynchronous operations. When we call a function, the call stack get occupied and will be free after function is called. Once page is loaded, call stack is free to handle events, timers, ajax, Promises and Async/await function used mainly as callbacks.

Microtask

High Priority Tasks like Promise, process.nextTick, queueMicrotask and async functions got first Priority as thet are Microtask.

Macrotask

Tasks such as Events, timers will be executes in event loop after Microtask. That is why Promises are always faster then setTimeout with 0 time.

Node JS is best for Data-Intensive or CPU Intensive Applications?

The use of single thread and asynchronous event-driven make Node JS best for Data Intensive Applications, like a Web Server where I/O is the biggest issue. Node JS servers best as a web server with very low memory and can server more requests.

Earlier Node JS was not best for CPU Intensive Applications where multi-threading is required. But Now Node JS supports Cluster and Worker modules for Multi threading and CPU Intensive Applications.

Node JS Vs PHP

Lets Compare Node JS Vs Php as a web server.

Php use Apache Web Server. Apache is Thread & Process Based server where each request is handled by a different thread (process). To assign process to different thread, Apache consumes more memory (RAM).

Node JS is based on Nginx. Nginx is a single thread web server used to handle multiple concurrent request.

Node JS Vs Apache Connections

Node JS Vs Apache Memory

Node JS vs Java vs Python

As php is only meant for web based applications, we can compare Node JS with Java and Python. Actually Java and Python are direct competitors or Node JS and they can build both Web and Desktop based applications.