Backend

Asynchronous JavaScript

• In general, Synchronous JavaScript reads line by line and executes the function.
• Synchronous js will directly execute in main stack.
• Meanwhile, if async js is present in the code, synchronous js execute directly in main stack while async js is moved to side stack.
• In side stack, the async code is processed but not executed.
• After the completion of every synchronous code in the main stack, async code is pushed to main stack then executed

async function test(){
const blob = await fetch ('https://randomuser.me/api/');
const result = await blob.json();
console.log(result);
}
test()

Node.js

• A javascript runtime environment
• A js wrapper built by 'Rahn dahl' to execute js code in v8 engine
• npm - node package manager
  • A playstore/ appstore for node and other js frameworks
  • install in https://www.npmjs.com

Modules

• Node.js comes default by many modules, popular ones;
  • HTTP
  • File system
  • Path

File System module (fs)

• It can be added by:

	const fs = require('fs');

• fs contains many API functions thats used to deal with backend problems
  • Using only a simple code we can create a file backup based on fs.writeFile() and fs.copyFile().

Handling with files in node.js can lead to debouncing, so its better to add debouncing function to the code to prevent debouncing

function debounce(func, timeout = 300){
  let timer;
  return (...args) => {
    clearTimeout(timer);
    timer = setTimeout(() => { func.apply(this, args); }, timeout);
  };
}

this debounce create a delay for the function, so that a single click cannot return with multiple responses.