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Running JavaScript Code

There are two primary ways to run JavaScript files locally once your environment is set up.

1. Running JS in the Browser​

To run your code in a browser, you need to connect your .js file to an HTML document using the <script> tag.

Step 1: Create index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>My JS App</title>
  </head>
  <body>
    <h1>Hello World</h1>
    <script src="app.js"></script>
  </body>
</html>

Step 2: Create app.js

console.log("JavaScript is running in the browser!");

Step 3: Open index.html in your browser and check the developer console!

2. Running JS via Node.js​

Running code via Node.js means you bypass the browser entirely. Since there's no browser, there's no DOM (Document Object Model), meaning you cannot manipulate HTML.

Step 1: Open your terminal and create a file.

// main.js
console.log("JavaScript is running locally via Node!");

Step 2: Execute the file using the node command.

node main.js