5 JavaScript concepts that every developer should know

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JavaScript is one of the most popular programming languages used primarily in web development. Today, I’ll share five concepts that I believe every web developer should be familiar with.

1. Hoisting

Hoisting in JavaScript is a behavior that moves declarations of classes, functions, variables, or imports to the top of their respective scopes (the top of the current script or function).

Variables:

Let’s see how hoisting impacts variables:

console.log(name) // undefined

var name;

As you can see, JavaScript allows us to reference the variable name before it's declared. This is because variable declarations are hoisted to the top of their respective scopes, giving them a default value of undefined

console.log(name) // ReferenceError: Cannot access 'name' before initialization

let name;

console.log(name) // ReferenceError: Cannot access 'name' before initialization

const name = 'John';

With let and const, the behavior is quite different. Since neither has a default value, referencing them before declaration results in a ReferenceError.

There’s an interesting behavior in the JavaScript interpreter.