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JavaScript Concepts: Learn the Basics

javascript concepts

JavaScript is an indispensable programming language for web development. This article covers seven fundamental JavaScript concepts that developers should master to build robust and efficient web applications.

Scopes and Closures

Scopes and closures are critical concepts in JavaScript that developers must comprehend. A scope is a code area where variables are declared and can be accessed. A closure is a function that has access to its parent function’s variables and parameters even after the parent function has returned.
One common use of closures is to create private variables and methods in JavaScript. By defining variables and functions within a closure, developers can ensure that they are only accessible within that closure, which provides a level of encapsulation and security.

Object-Oriented Programming

JavaScript is a versatile programming language that supports both functional and object-oriented programming paradigms. Object-oriented programming is a programming paradigm that employs objects to represent data and methods to perform operations on that data.
In JavaScript, objects can be created using object literal notation or constructor functions. Prototypal inheritance can also be used to create new objects based on existing objects.

Async and Promises

Asynchronous programming is a technique employed in JavaScript to perform time-consuming operations without blocking the primary thread. Asynchronous code executes in the background, and when it’s finished, it runs a callback function.
Promises are a recent addition to JavaScript that provides a more sophisticated way of handling asynchronous code. Promises enable developers to chain asynchronous operations and handle errors in a more readable and concise manner.

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Callbacks are functions that are passed as arguments to other functions and are executed when the function completes its task. Callbacks are often used in JavaScript to perform asynchronous operations and handle events.
One advantage of using callbacks is that they allow developers to write modular and reusable code. By passing a callback function as an argument, they can decouple the code that invokes the function from the code that handles the result.

Example Code

function myFirst() {
function myDisplayer(some){

Event Loop

The event loop is a crucial concept in JavaScript that developers must understand. The event loop handles events and executes callbacks in an asynchronous environment.
The event loop runs continuously, monitoring the call stack and the task queue in JavaScript. When the call stack is empty, it checks the task queue for any pending tasks and executes them in the order they were added.

Example Code

console.log("Before delay"); 
function delayBySeconds(sec) {
   let start = now =
   while(now-start < (sec*1000)) {
     now =;
console.log("After delay");


Before code is executed in JavaScript, variable and function declarations are hoisted to the top of their scope. This means that a variable or function can be used before it has been declared.
Although hoisting can be beneficial, it can also result in unexpected behavior if not understood correctly. Developers must declare variables and functions before using them to avoid any issues.

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Higher-Order Functions

Higher-order functions are functions that can take other functions as arguments or return functions as results. Higher-order functions are a powerful tool in JavaScript that can simplify complex code and provide a more functional programming style.
Developers can use higher-order functions to create reusable functions that can operate on different data types. By passing a function as an argument, they can create a more flexible and modular codebase.

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In conclusion, mastering these seven JavaScript concepts is essential to build robust and efficient web applications. Developers who comprehend these concepts can develop scalable and maintainable web applications. This article aims to provide a comprehensive overview of these concepts to help…