What is JavaScript and Running It

Site Admin · 11 Sep 2026 · 8 views

What is JavaScript and Running It

JavaScript is the programming language of the web. It runs in every browser, enabling interactive pages, dynamic content, and complex applications. With Node.js, it also runs on the server.

A Brief History

JavaScript was created in 1995 by Brendan Eich at Netscape in just ten days. Despite its rushed origin, it evolved into the most widely used programming language in the world. Modern JavaScript (ES6+) is powerful, expressive, and nothing like the language of the 1990s.

Running JavaScript in the Browser

Add a <script> tag in your HTML. The browser executes the code when it reaches the tag.

<!DOCTYPE html>
<html lang="en">
<head><title>JS Demo</title></head>
<body>
    <h1 id="greeting">Hello</h1>
    <script>
        document.getElementById("greeting").textContent = "Hello, JavaScript!";
    </script>
</body>
</html>

Running JavaScript with Node.js

Node.js lets you run JavaScript outside the browser. Install it, create a .js file, and run it from the terminal:

// hello.js
const name = "World";
console.log(`Hello, ${name}!`);

Run it with node hello.js and the output is Hello, World!.

The Console

The console object is your primary debugging tool. It works in both browsers and Node.js.

console.log("Simple message");
console.info("Informational");
console.warn("Warning!");
console.error("Something broke");
console.table([{name: "Alice", age: 30}, {name: "Bob", age: 25}]);