Jeromy  Lowe

Jeromy Lowe

1595553079

Intro to Callback in JavaScript

During my journey of learning JavaScript and a few days in with React, I had to come to terms with callback functions. It was impossible to avoid its existence and blindly using it without understanding. To understand callback function we have to know a bit about functions. Here I want to talk about function expression, arrow function, and callback function.


What is a Callback function?

According to MDN doc:

A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action.

In JavaScript, functions are objects, which means, like any other objects it can be assigned to a variable and passed as an argument to another function. In a nutshell, a callback function is a function that is provided as a parameter for other methods such as forEach method or addEventListener method and gets invoked at a certain point in time.

Passing functions as arguments

So how do we do this? Let’s see with an example below:

document.addEventListener(‘click’,whoAmI);

//whoAmI Function Declaration(Function Statement)
function whoAmI(event){
  console.log(event.target.tagName)
}

We attached the ‘click’ event listener to document with whoAmI function as a parameter that logs the tag name of the clicked target. Whenever ‘click’ happens whoAmI function will be called with an _event_ argument. We call whoAmI a callback function.

When we call a function by its name followed by ( ), we are telling the function to execute its code. When we name a function or pass a function without the ( ), the function does not execute.** The callback function doesn’t execute right away. Instead, the addEventListener method executes the function when the event occurs.**

One more thing I want to mention is because we used function declaration, we were able to call thewhoAmI function before it was declared. It’s the magic of hoisting in JS. But with function expression, it doesn’t get hoisted. So the order of writing function expressions and using them as callback would be crucial.

#callback #javascript #callback-function #function #javascript-fundamental

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Intro to Callback in JavaScript
Jeromy  Lowe

Jeromy Lowe

1595553079

Intro to Callback in JavaScript

During my journey of learning JavaScript and a few days in with React, I had to come to terms with callback functions. It was impossible to avoid its existence and blindly using it without understanding. To understand callback function we have to know a bit about functions. Here I want to talk about function expression, arrow function, and callback function.


What is a Callback function?

According to MDN doc:

A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action.

In JavaScript, functions are objects, which means, like any other objects it can be assigned to a variable and passed as an argument to another function. In a nutshell, a callback function is a function that is provided as a parameter for other methods such as forEach method or addEventListener method and gets invoked at a certain point in time.

Passing functions as arguments

So how do we do this? Let’s see with an example below:

document.addEventListener(‘click’,whoAmI);

//whoAmI Function Declaration(Function Statement)
function whoAmI(event){
  console.log(event.target.tagName)
}

We attached the ‘click’ event listener to document with whoAmI function as a parameter that logs the tag name of the clicked target. Whenever ‘click’ happens whoAmI function will be called with an _event_ argument. We call whoAmI a callback function.

When we call a function by its name followed by ( ), we are telling the function to execute its code. When we name a function or pass a function without the ( ), the function does not execute.** The callback function doesn’t execute right away. Instead, the addEventListener method executes the function when the event occurs.**

One more thing I want to mention is because we used function declaration, we were able to call thewhoAmI function before it was declared. It’s the magic of hoisting in JS. But with function expression, it doesn’t get hoisted. So the order of writing function expressions and using them as callback would be crucial.

#callback #javascript #callback-function #function #javascript-fundamental

Rahul Jangid

1622207074

What is JavaScript - Stackfindover - Blog

Who invented JavaScript, how it works, as we have given information about Programming language in our previous article ( What is PHP ), but today we will talk about what is JavaScript, why JavaScript is used The Answers to all such questions and much other information about JavaScript, you are going to get here today. Hope this information will work for you.

Who invented JavaScript?

JavaScript language was invented by Brendan Eich in 1995. JavaScript is inspired by Java Programming Language. The first name of JavaScript was Mocha which was named by Marc Andreessen, Marc Andreessen is the founder of Netscape and in the same year Mocha was renamed LiveScript, and later in December 1995, it was renamed JavaScript which is still in trend.

What is JavaScript?

JavaScript is a client-side scripting language used with HTML (Hypertext Markup Language). JavaScript is an Interpreted / Oriented language called JS in programming language JavaScript code can be run on any normal web browser. To run the code of JavaScript, we have to enable JavaScript of Web Browser. But some web browsers already have JavaScript enabled.

Today almost all websites are using it as web technology, mind is that there is maximum scope in JavaScript in the coming time, so if you want to become a programmer, then you can be very beneficial to learn JavaScript.

JavaScript Hello World Program

In JavaScript, ‘document.write‘ is used to represent a string on a browser.

<script type="text/javascript">
	document.write("Hello World!");
</script>

How to comment JavaScript code?

  • For single line comment in JavaScript we have to use // (double slashes)
  • For multiple line comments we have to use / * – – * /
<script type="text/javascript">

//single line comment

/* document.write("Hello"); */

</script>

Advantages and Disadvantages of JavaScript

#javascript #javascript code #javascript hello world #what is javascript #who invented javascript

Hire Dedicated JavaScript Developers -Hire JavaScript Developers

It is said that a digital resource a business has must be interactive in nature, so the website or the business app should be interactive. How do you make the app interactive? With the use of JavaScript.

Does your business need an interactive website or app?

Hire Dedicated JavaScript Developer from WebClues Infotech as the developer we offer is highly skilled and expert in what they do. Our developers are collaborative in nature and work with complete transparency with the customers.

The technology used to develop the overall app by the developers from WebClues Infotech is at par with the latest available technology.

Get your business app with JavaScript

For more inquiry click here https://bit.ly/31eZyDZ

Book Free Interview: https://bit.ly/3dDShFg

#hire dedicated javascript developers #hire javascript developers #top javascript developers for hire #hire javascript developer #hire a freelancer for javascript developer #hire the best javascript developers

Niraj Kafle

1589255577

The essential JavaScript concepts that you should understand

As a JavaScript developer of any level, you need to understand its foundational concepts and some of the new ideas that help us developing code. In this article, we are going to review 16 basic concepts. So without further ado, let’s get to it.

#javascript-interview #javascript-development #javascript-fundamental #javascript #javascript-tips

Lenora  Hauck

Lenora Hauck

1598718780

An Intro to JavaScript Modules

There seems to be some confusion when it comes to JavaScript modules and how they exactly work, and why are there different forms in which we can use them. Today I’ll explain the different ways in which you can export and import modules.

Some background on JavaScript modules

JavaScript programs started as simple scripts or apps with rather small codebases, but as it has been evolving and so its uses have been increasing the size of the codebases have increased drastically. To support this increase the language needed to support a mechanism under which was possible to separate or split the code into smaller, reusable units. Node.JS had that ability for a while before it was incorporated in JavaScript with a feature called modules. And thus eventually they made it to the language itself and the browsers.

By definition, a module is just a file which can be imported from other modules (or files) through the help of directives like export and import:

  • export: keyword labels variables and functions that should be accessible from outside the current module.
  • import: allows the import of functionality from other modules.

We’ll come back to more of that later.


Introducing an example

To demonstrate the use of modules we will create a simple user module that will expose a User class. Let’s review the basic structure for the project:

index.html
scripts/
    index.js
    modules/
        user.js

Our app will be very simple and it will just show the name of a user on the screen, but the interesting part is that the name will come from an object instance of the User class. Let’s see it in action with a live demo:

#javascript #intro to javascript #background on javascript