The Ultimate Asynchronous Javascript Functions Guide in 2020

In this article, we shortly recap synchronous functions and then head over the asynchronous functions in JavaScript, and at the end of this article, you understand asynchronous javascript functions!

Synchronous JavaScript

To understand what asynchronous JavaScript is, we need to know what synchronous JavaScript is.

const btn = document.querySelector('button');
btn.addEventListener('click', () => {
  alert('You clicked me!');

  let pElem = document.createElement('p');
  pElem.textContent = 'This is a newly-added paragraph.';
  document.body.appendChild(pElem);
});

While each operation is being processed, nothing else can happen, rendering is paused. Only one thing can happen at a time, on a single main thread, and everything else is blocked until the operation completes.

Asynchronous JavaScript

A lot of web API’s require asynchronous code to be able to run. Mostly when fetching data from an external service such as a network.

With asynchronous data, you can’t just fetch data from the source, for example, if you want to use an image you can immediately after you call the fetch to use the data since you don’t know how long it takes to download the image.

With Async, javascript comes that there are two methods to handle asynchronous data.

Async Callbacks

Async callbacks are functions that are specified as arguments when calling a function which will start executing code in the background.

btn.addEventListener('click', () => {
  alert('You clicked me!');

  let pElem = document.createElement('p');
  pElem.textContent = 'This is a newly-added paragraph.';
  document.body.appendChild(pElem);
});

#api #tech #javascript #programming #asynchronous-javascript

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Citrix Bugs Allow Unauthenticated Code Injection, Data Theft

Multiple vulnerabilities in the Citrix Application Delivery Controller (ADC) and Gateway would allow code injection, information disclosure and denial of service, the networking vendor announced Tuesday. Four of the bugs are exploitable by an unauthenticated, remote attacker.

The Citrix products (formerly known as NetScaler ADC and Gateway) are used for application-aware traffic management and secure remote access, respectively, and are installed in at least 80,000 companies in 158 countries, according to a December assessment from Positive Technologies.

Other flaws announced Tuesday also affect Citrix SD-WAN WANOP appliances, models 4000-WO, 4100-WO, 5000-WO and 5100-WO.

Attacks on the management interface of the products could result in system compromise by an unauthenticated user on the management network; or system compromise through cross-site scripting (XSS). Attackers could also create a download link for the device which, if downloaded and then executed by an unauthenticated user on the management network, could result in the compromise of a local computer.

“Customers who have configured their systems in accordance with Citrix recommendations [i.e., to have this interface separated from the network and protected by a firewall] have significantly reduced their risk from attacks to the management interface,” according to the vendor.

Threat actors could also mount attacks on Virtual IPs (VIPs). VIPs, among other things, are used to provide users with a unique IP address for communicating with network resources for applications that do not allow multiple connections or users from the same IP address.

The VIP attacks include denial of service against either the Gateway or Authentication virtual servers by an unauthenticated user; or remote port scanning of the internal network by an authenticated Citrix Gateway user.

“Attackers can only discern whether a TLS connection is possible with the port and cannot communicate further with the end devices,” according to the critical Citrix advisory. “Customers who have not enabled either the Gateway or Authentication virtual servers are not at risk from attacks that are applicable to those servers. Other virtual servers e.g. load balancing and content switching virtual servers are not affected by these issues.”

A final vulnerability has been found in Citrix Gateway Plug-in for Linux that would allow a local logged-on user of a Linux system with that plug-in installed to elevate their privileges to an administrator account on that computer, the company said.

#vulnerabilities #adc #citrix #code injection #critical advisory #cve-2020-8187 #cve-2020-8190 #cve-2020-8191 #cve-2020-8193 #cve-2020-8194 #cve-2020-8195 #cve-2020-8196 #cve-2020-8197 #cve-2020-8198 #cve-2020-8199 #denial of service #gateway #information disclosure #patches #security advisory #security bugs

The Difference Between Regular Functions and Arrow Functions in JavaScript

Other then the syntactical differences. The main difference is the way the this keyword behaves? In an arrow function, the this keyword remains the same throughout the life-cycle of the function and is always bound to the value of this in the closest non-arrow parent function. Arrow functions can never be constructor functions so they can never be invoked with the new keyword. And they can never have duplicate named parameters like a regular function not using strict mode.

Here are a few code examples to show you some of the differences

this.name = "Bob";
const person = {

name: “Jon”,
<span style="color: #008000">// Regular function</span>
func1: <span style="color: #0000ff">function</span> () {
    console.log(<span style="color: #0000ff">this</span>);
},

<span style="color: #008000">// Arrow function</span>
func2: () =&gt; {
    console.log(<span style="color: #0000ff">this</span>);
}

}
person.func1(); // Call the Regular function

// Output: {name:“Jon”, func1:[Function: func1], func2:[Function: func2]}
person.func2(); // Call the Arrow function

// Output: {name:“Bob”}

The new keyword with an arrow function

const person = (name) => console.log("Your name is " + name);
const bob = new person("Bob");
// Uncaught TypeError: person is not a constructor

If you want to see a visual presentation on the differences, then you can see the video below:

#arrow functions #javascript #regular functions #arrow functions vs normal functions #difference between functions and arrow functions

The Ultimate Asynchronous Javascript Functions Guide in 2020

In this article, we shortly recap synchronous functions and then head over the asynchronous functions in JavaScript, and at the end of this article, you understand asynchronous javascript functions!

Synchronous JavaScript

To understand what asynchronous JavaScript is, we need to know what synchronous JavaScript is.

const btn = document.querySelector('button');
btn.addEventListener('click', () => {
  alert('You clicked me!');

  let pElem = document.createElement('p');
  pElem.textContent = 'This is a newly-added paragraph.';
  document.body.appendChild(pElem);
});

While each operation is being processed, nothing else can happen, rendering is paused. Only one thing can happen at a time, on a single main thread, and everything else is blocked until the operation completes.

Asynchronous JavaScript

A lot of web API’s require asynchronous code to be able to run. Mostly when fetching data from an external service such as a network.

With asynchronous data, you can’t just fetch data from the source, for example, if you want to use an image you can immediately after you call the fetch to use the data since you don’t know how long it takes to download the image.

With Async, javascript comes that there are two methods to handle asynchronous data.

Async Callbacks

Async callbacks are functions that are specified as arguments when calling a function which will start executing code in the background.

btn.addEventListener('click', () => {
  alert('You clicked me!');

  let pElem = document.createElement('p');
  pElem.textContent = 'This is a newly-added paragraph.';
  document.body.appendChild(pElem);
});

#api #tech #javascript #programming #asynchronous-javascript

Function Expression vs Function Declaration in JavaScript

Function Expression vs Function Declaration in JavaScript.

It was until during one of the JavaScript mock interviews did I came across the term function expression.

The question was: What is the difference between these two syntax?

function x(){

}

let x = function(){

}

I was clueless for a moment. After thinking a little, I could only come up with: the second syntax invokes an _anonymous _function and is assigned to a variable.

I was alien to the term hoisting.

In this article, we will acquaint ourselves with three simple terms: function declaration,_ function expression, _and hoisting.

What is function declaration?

Function declaration is also known as _function statement. _It contains the name of the function, parameters, and a return statement. **Naming the function **is what sets function declaration apart. Parameters and return statement is optional.

Function Declaration

What is function expression?

Function expression also has a name, parameters, and return statement. All of which are optional. The important thing to bear in mind is: the function here is _assigned _to a JavaScript variable.

Function Expression

#function-expression #function-declaration #functions-in-javascript #coding #javascript #express

JavaScript Factory Functions

JavaScript factory functions made simple.

📺 The video in this post was made by Programming with Mosh
The origin of the article: https://www.youtube.com/watch?v=jpegXpQpb3o&list=PLTjRvDozrdlxEIuOBZkMAK5uiqp8rHUax&index=9
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