Closures Explained in 100 Seconds // Tricky JavaScript Interview Prep

What is a JavaScript Closure? Learn the how closures allow functions to “remember” outside their local scope

🔗 Resources

MDN Docs https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures
My Favorite Closure Explanation https://stackoverflow.com/a/36879264/3808414
Interview Question https://dmitripavlutin.com/simple-but-tricky-javascript-interview-questions/

#javascript

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Closures Explained in 100 Seconds // Tricky JavaScript Interview Prep

What is a JavaScript Closure? Learn the how closures allow functions to “remember” outside their local scope

🔗 Resources

MDN Docs https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures
My Favorite Closure Explanation https://stackoverflow.com/a/36879264/3808414
Interview Question https://dmitripavlutin.com/simple-but-tricky-javascript-interview-questions/

#javascript

A practical example of Javascript closures

ost developers today, know about closures in Javascript. Don’t be sad if you don’t, it’s not something you generally use on your every-day work (well, you may, but it’s not so common).

losures are something that many companies would like you to know before working for them, therefore, chances are they’ll ask you something related with this topic, or even more, they could make you write a practical example of it.

On this story, I’m gonna tell you about a small function I was asked to develop on an interview a while ago, that involved the use of closures for its solution.

Let’s start with the premise:

Can you write a function that will solve the following test case?

let result = sum(1)(2)(3)();

console.log(result === 6 ? 'SUCCESS' : 'ERROR');

The function we need to create will sum the values sent as a parameter and will accumulate them. Also, it will return another function for the next value to be passed on. If we don’t send any value to it, it will return the accumulated value.

It looks fairly simple at first, but let’s take a look into it:

const sum = (value) => {
  let accum = 0;

  if (value) {
    accum += value;
    const innerSum = (value) => { /*TODO*/ };
  } else {
    return accum;
  }
};
console.log(sum());
0

That’s a good start. First, we create the function called sum that will take a value as a parameter. If that value exists, we will sum the value to the accum and return a function to keep adding values (TODO).

#currying #javascript-interview #javascript #closures-functions #closure

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

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

7 Interview Questions on JavaScript Closures. Can You Answer Them?

Every JavaScript developer must know what a closure is. During a JavaScript coding interview there’s a good chance you’ll get asked about the concept of closures.

I compiled a list of 7 interesting and increasingly challenging questions on JavaScript closures.

Take a pencil and a piece of paper, and try to answer the questions without looking at the answers, or running the code. In my estimation, you would need about 30 minutes.

Have fun!

Questions 1: Closures raise your hand

Consider the following functions clickHandler, immediate, and delayedReload:

let countClicks = 0;
button.addEventListener('click', function clickHandler() {
  countClicks++;
});
const result = (function immediate(number) {
  const message = `number is: ${number}`;
  return message;
})(100);
setTimeout(function delayedReload() {
  location.reload();
}, 1000);

#javascript #closure #interview