Learn these 6 concepts that every JavaScript developer should understand.

6 JavaScript Concepts a Web Developer Should Understand

JavaScript is one of the most important programming languages used in software development. It is also one of the three important languages all web developers must learn, alongside HTML and CSS. JavaScript is used to program the behavior of web pages, incorporating third-party libraries.

The foremost thing about learning JavaScript development is starting with the basics and learning the core features of JavaScript. However, if you want to become a successful JavaScript web developer there are a few concepts you need to understand.

Below, we introduce the six most important JavaScript concepts every web developer should know.


The first thing you should master is prototypes because it’s inherent in every object in JavaScript. And as you may already know, almost everything in this programming language is an object. One way to create objects in JavaScript is the constructor function. However, every object in JavaScript has its own methods and properties.

For example, two objects can have two instances of the constructor function but it won’t make sense to have a copy of that constructor function doing the same thing. Instead, we use the prototype property of a construction function. Since this prototype is connected with each object, your problem is solved.


The scope is variable access, meaning a set of rules for where and how variables are stored. In JavaScript, you’re always in the root scope, also known as the window scope. It is simply a box with a boundary for variables, objects, and functions. The boundaries put restrictions on the variables and determine if you have access to it or not. In other words, it limits the availability and visibility of a variable to the other parts of the code.

A scope can be local or global. The local scope allows access to everything inside the box, while the global scope is everything outside the box. Note that a global scope cannot access a variable in the local scope as it is enclosed from the outer world, except if you return it. Keep in mind that understanding the scope will make learning JavaScript easier for you as it is the best place to start getting a hang of the foundations of JavaScript.


An immediately invoked function expression (IIFE) executes functions immediately, as soon as they are created. Variables that are declared within the IIFE cannot be accessed by the global scope (outside world), meaning you can avoid the global scope from being polluted.

The main reason to use this is to obtain data privacy and execute the code. This means that if you want to invoke the function expression instantly, you just need to tackle a couple of parentheses on the end.


Many developers get unexpected results when they’re not clear about the concept of hoisting in JavaScript. In this programming language, you can call a function before it is defined and you won’t experience an error. The reason for this is hoisting where the JavaScript interpreter moves the functions and variables declaration to the top of the current scope, before the code execution.

Note that JavaScript only hoists declarations but not initialization. Other things you need to know about hoisting include hoisting functions and classes, as well as let, var, and const keywords in JavaScript (ES6).

Classes (ES6)

In recent years, one of the most noticeable changes in JavaScript has been the introduction of classes. Classes (ES6) are so-called syntactic sugar, and they’re based on JavaScript’s existing prototypal inheritance. They’re defined as special functions, and the class syntax has two components including class expressions and class declarations.

Learning about issues such as inheritance, objects, instances, and encapsulation are the most important elements of the most popular programming paradigm—object-oriented programming.


This is a function inside another function and has access to the outer function variable. It is also called the inner function, as it can access the variable defined in its scope, meaning the scope of its parent function and the global variables. However, keep in mind that the outer function cannot have access to the inner function variable.

The reason you should understand closures is that they’re used when you want to extend behavior such as methods, passing variables, or arrays from an outer function to an inner function. Although JavaScript is not a pure object-oriented language, you can achieve object-oriented behavior through closures.

JavaScript Closures

Final thoughts

JavaScript is an essential programming language for web developers who are interested in building custom web, mobile, and desktop applications. The concepts mentioned above are some of the most important every JavaScript developer should understand. Make sure you consult an expert to educate you, so you can get a better understanding of the overall concept of JavaScript development.

Senior Software Engineer at Software Medico. Interested in programming since he was 14 years old, Carlos is a self-taught programmer and founder and author of most of the articles at Our Code World.