JavaScript (often abbreviated as JS) is the "language of the web." It is a versatile, high-level, and multi-paradigm programming language that powers the interactivity you see on almost every website today.
Here is a comprehensive breakdown of everything you need to know about JavaScript.
Originally created in just 10 days by Brendan Eich in 1995 for Netscape Navigator, JavaScript has evolved from a simple scripting tool into a powerhouse of modern software development.
Standardization: It is standardized by ECMAScript (ES). The most significant update was ES6 (2015), which introduced modern syntax like classes and arrow functions.
Engine: Browsers use engines to execute JS code. The most famous is Google’s V8 engine, which also powers Node.js.
JavaScript is unique because of how it handles data and execution:
High-Level: It abstracts away complex computer memory management (garbage collection).
Just-In-Time (JIT) Compiled: While often called "interpreted," modern engines compile JS into machine code right before execution for speed.
Single-Threaded: It executes one command at a time.
Non-blocking I/O: Using an Event Loop, it can handle multiple tasks (like fetching data) without freezing the user interface.
JavaScript works alongside HTML and CSS to create the web experience:
HTML: The structure (the "skeleton").
CSS: The styling (the "skin and clothes").
JavaScript: The behavior (the "muscles and brain"). It allows for things like dropdown menus, form validation, and real-time updates without refreshing the page.
To give you a feel for the language, here is a snippet showing variables, a function, and a simple logic check:
JavaScript
// A simple function to greet a user
function greetUser(name) {
const message = "Hello, " + name + "!";
if (name === "Admin") {
console.log(message + " Welcome to the dashboard.");
} else {
console.log(message);
}
}
greetUser("Gemini"); // Output: Hello, Gemini!
o create a script that interacts with a user, displays a result on the screen, and sends it to a printer, we use a combination of JavaScript for the logic and HTML for the user interface.
Since JavaScript runs in the browser, the "printer" functionality is handled by the window.print() method, which opens the browser's print dialog.
Here is a complete, single-file solution. You can save this code as an .html file (e.g., multiply.html) and open it in any browser.
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Multiplication Tool</title>
<style>
body { font-family: sans-serif; padding: 20px; line-height: 1.6; }
.container { max-width: 400px; margin: auto; border: 1px solid #ccc; padding: 20px; border-radius: 8px; }
input { width: 100%; padding: 8px; margin: 10px 0; box-sizing: border-box; }
button { width: 100%; padding: 10px; cursor: pointer; background-color: #28a745; color: white; border: none; border-radius: 4px; }
button:hover { background-color: #218838; }
#result { margin-top: 20px; font-weight: bold; font-size: 1.2em; color: #007bff; }
/* This hides the input form when printing, so only the result shows */
@media print {
.no-print { display: none; }
#result { font-size: 24pt; text-align: center; margin-top: 50px; }
}
</style>
</head>
<body>
<div class="container no-print">
<h2>Multiplier</h2>
<label>Enter First Number:</label>
<input type="number" id="num1" placeholder="e.g. 5">
<label>Enter Second Number:</label>
<input type="number" id="num2" placeholder="e.g. 10">
<button onclick="calculateAndPrint()">Calculate & Print</button>
</div>
<div id="result"></div>
<script>
function calculateAndPrint() {
// 1. Store the inputs in variables
const n1 = document.getElementById('num1').value;
const n2 = document.getElementById('num2').value;
// 2. Validate and Multiply
if (n1 === "" || n2 === "") {
alert("Please enter both numbers");
return;
}
const product = n1 * n2;
// 3. Output to the display screen
const displayArea = document.getElementById('result');
displayArea.innerHTML = `Result: ${n1} × ${n2} = ${product}`;
// 4. Output to the printer
// We use a small timeout to ensure the screen updates before the print dialog opens
setTimeout(() => {
window.print();
}, 500);
}
</script>
</body>
</html>