JavaScript Basics

What is JavaScript?

JavaScript is the programming language of the web. It runs in the browser and lets you make pages interactive — responding to clicks, updating content, and communicating with servers.

Adding JavaScript to a Page

Place your script in a script tag at the bottom of your HTML body.

Or link to an external file.

Variables

Use let and const to declare variables.

let name = "Alice";

const age = 25;

Functions

Define reusable blocks of code with functions.

function greet(name) {

return "Hello, " + name + "!";

}

console.log(greet("Alice"));

DOM Manipulation

Use JavaScript to interact with HTML elements.

const heading = document.getElementById("main-heading");

heading.textContent = "Updated by JavaScript!";

heading.style.color = "red";

Events

Respond to user actions like clicks.

const btn = document.getElementById("my-button");

btn.addEventListener("click", function() {

alert("Button clicked!");

});

Conditionals and Loops

JavaScript supports the same logic structures as other languages.

if (age >= 18) {

console.log("Adult");

}

for (let i = 0; i < 5; i++) {

console.log(i);

}

Next Steps

Learn about fetch for API calls, ES6 arrow functions, and frameworks like React.