JavaScript - The Basics

Web Development Overview

Web development involves writing a lot of HTML, CSS and JS code.

Historically (and even today to some extent), browsers could only understand HTML, CSS and JS.

Any website that you see is a bunch of HTML, CSS and JS files along with some assets (images, videos etc).

<aside> Important Facts:

• React, NextJS are frameworks. They compile down to HTML, CSS, JS in the end. That is what your browser understands.
• When you run your C++ code on leetcode, it does not run on your browser/machine. It runs somewhere else. Your browser can't (almost) compile and run C++ code.
• If someone asks — What all languages can your browser interpret, the answer is HTML, CSS, JS and WebAssembly. It can, technically, run C++/Rust code that is compiled down to Wasm. </aside>

Properties of JavaScript

Every language comes with its unique set of features. JavaScript has the following:

1. Interpreted Language

JavaScript is an interpreted language, meaning it's executed line-by-line at runtime by the JavaScript engine in the browser or server environment, rather than being compiled into machine code beforehand.

• Upsides and Downsides

2. Dynamically Typed

Variables in JavaScript are not bound to a specific data type. Types are determined at runtime and can change as the program executes.

// C++ Code (won't compile)
#include <iostream>

int main() {
    int a = 1;
    a = "hello";  // Error
    a = true;     // Error
}

// JS Code (will compile)
var a = 1;
a = "harkirat";
a = true;

console.log(a)