10 JavaScript Concepts Every Junior Developer Should Know

JavaScript is like the engine behind how websites work. It makes things move and change when you use them. For new developers just starting, it’s really important to learn some basic stuff about JavaScript. This will help you understand how it works and get ready for more advanced stuff later on. Here are the top 10 things you should learn first if you’re just getting into JavaScript.

Variables and Data Types

In programming, variables are like basic tools you use all the time. In JavaScript, you can create them using words like var, let, or const. Knowing what makes these words different is important. For instance, let and const came out in ECMAScript 6 and works inside specific blocks of code, while var only works inside functions. Picking the right type of variable depends on what you’re doing.

Scope

Understanding scope can be tough for new JavaScript developers, but it’s really important. There are two types: global and local. Global means a variable can be used anywhere in the code, while local means it’s only available within a specific function. It might sound simple, but the scope can get more complicated. Learning about it early on can help you as you keep learning and become a better web developer.

DOM and Layout Trees

The Document Object Model, usually referred to as the DOM, is an essential part of making websites interactive. It is an interface that allows a programming language to manipulate the content, structure, and style of a website. JavaScript is the client-side scripting language that connects to the DOM in an internet browser.

Closures​

Closures are like special functions that can remember where they came from, even when that place is gone. They’re handy because they help keep information private and let you use cool programming tricks.

Prototypal Inheritance

Prototypal inheritance is a big idea in JavaScript. It lets objects borrow stuff, like properties and actions, from other objects. Every object in JavaScript has a special prototype object it can borrow from.

Asynchronous JS

It’s important to understand how the event loop works. It’s like knowing how the browser handles things like when you click on stuff, ask for stuff from the web, or do other actions. You should also know about writing code that doesn’t always run in order, called asynchronous code. And remember, JavaScript does things one at a time, but it can still handle many things happening at once.

Conditional Statements

Conditional statements are like the brain of your code. They help it make decisions. For example, if something is true, do one thing; otherwise, do another. These statements let your code react differently depending on what’s happening, which helps you control how your code behaves in different situations.

Hoisting

If you’re used to another language, hoisting might seem like magic. It lets you use variables and functions before you even declare them! It’s called “hoisting” because it’s like the interpreter lifts these things up to the top of the code. This helps prevent errors when running your code. But remember, hoisting only works with functions and variables declared with ‘var’. If you use ‘const’ or ‘let’, the interpreter won’t hoist them up for you.

Callback Functions

JavaScript callback functions can seem scary to a lot of folks, but they’re actually pretty simple. Check this out: in this example, the console.log function is passed as a callback to myFunc. It just means that it’ll run after setTimeout finishes its job.

function myFunc(text, callback) {setTimeout(function() {callback(text);}, 2000);}

myFunc(‘Hello world!’, console.log);// ‘Hello world!’

Destructuring

Destructuring means breaking down an array or object into smaller pieces. It helps us take values from objects and arrays and put them into separate variables easily. Using destructuring made our code neater and saved us three lines of code.

If you didn’t know any of these 10 concepts before, you’ve probably learned something new about JavaScript! And if you already knew them all, then hopefully, this was a good opportunity to brush up and expand your knowledge.