Joel Kelly

Joel Kelly

1571282940

Async Functions in JavaScript

Async functions were introduced in the 2017 edition of the JavaScript language spec. Async functions differ from normal JavaScript functions in 2 major ways:

  • JavaScript ensures that an async function always returns a promise.
  • You can only use the await operator in the body of an async function.

Async functions allow you to write asynchronous code that looks synchronous. In this article, you’ll learn the basics of what makes async functions special.

Using await

Given a promise p, the await operator pauses execution of your async function until p is settled. For example, the below code will print “Hello World” after 1 second.

async function run() {
  // Pause execution for 1 second
  await new Promise(resolve => setTimeout(resolve, 1000));
  console.log('Hello, World');
}

run();

A promise can be in one of 3 states: pending, fulfilled, or rejected. A promise is considered settled once it is either fulfilled or rejected. In the above example, the promise is in the pending state for 1 second, and then resolve() transitions the promise to the fulfilled state. Below is a diagram of the possible states a promise can be in.

The most powerful feature of await is that you can use it in conjunction with for loops and if statements. For example, the below code will print ‘1’ and ‘2’, wait 1 second, then print ‘3’ and ‘4’, and so on up to ‘9’ and ‘10’.

async function run() {
  for (let i = 1; i <= 10; ++i) {
    if (i % 2 === 0) {
      // Pause execution for 1 second
      await new Promise(resolve => setTimeout(resolve, 1000));
    }
    console.log(i);
  }
}

run();

#javascript #programming #developer

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Async Functions in JavaScript
Vincent Lab

Vincent Lab

1605017502

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

Madyson  Reilly

Madyson Reilly

1601069940

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.

Image for post

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.

Image for post

Function Expression

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

Lowa Alice

Lowa Alice

1624410000

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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#javascript #factory functions #functions #javascript factory functions

Lowa Alice

Lowa Alice

1624392000

JavaScript Constructor Functions. IN JUST 6 MINUTES!!!

JavaScript Constructor 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=23AOrSN-wmI&list=PLTjRvDozrdlxEIuOBZkMAK5uiqp8rHUax&index=10
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☞ **-----CLICK HERE-----**⭐ ⭐ ⭐
Thanks for visiting and watching! Please don’t forget to leave a like, comment and share!

#javascript #functions #constructor #constructor functions #javascript constructor functions

Giles  Goodwin

Giles Goodwin

1603176407

The real reason why JavaScript has arrow functions

Nowadays, all my code is based on the use of arrow functions. If you are still not using them yourself, then don’t be ashamed of who you are. That’s your parent’s job. Instead, find about all the benefits that you can get by using arrow functions like the cool kids.

This is an example of arrow function and the same code written traditionally:

const arrowFunction = (arg1, arg2) => arg1 + arg 2;

const traditionalFunction = function(arg1, arg2) {
  return arg1 + arg2;
};

You may notice that the code is shorter and that there is an arrow. Everything before the arrow is arguments of the function and everything after the arrow is always returned as the result of the function.

If you need a function that contains multiple statements you can still do this:

const arrowFunction = (arg1, arg2) => {
  const result = arg1 + arg2;
  return result;
};

#javascript #js #functional-javascript #functional-programming #javascript-tips