JavaLearn/variables.html at master · jhavishesh7/JavaLearn · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Variables & Data Types - JavaScript Mastery</title>
  <style>
    body { background: #121212; color: #fff; font-family: sans-serif; padding: 20px; }
    pre { background: #1e1e1e; padding: 10px; border-radius: 5px; margin-bottom: 20px; }
    .output { background: #222; color: #b9f6ca; padding: 12px; border-radius: 5px; min-height: 40px; margin-bottom: 20px; white-space: pre-line; }
    .btn { display: inline-block; background: #4caf50; color: white; font-size: 1.1em; padding: 10px 24px; border-radius: 6px; text-decoration: none; margin-top: 20px; }
    .btn:hover { background: #388e3c; }
    .explanation { background: #263238; color: #ffe082; border-radius: 6px; padding: 18px; margin-top: 30px; font-size: 1.08em; line-height: 1.7; }
    .explanation h2 { color: #ffd600; margin-top: 0; }
  </style>
</head>
<body>
  <h1>Variables & Data Types</h1>
  <pre><code>let name = "Alice";
let age = 25;
let isStudent = true;
let nothing = null;
let notDefined;
let bigNumber = 12345678901234567890n;
let sym = Symbol('unique');

let person = { name: "Bob", age: 30 };
let numbers = [1, 2, 3];

let output = `Name: ${name}, Type: ${typeof name}
Age: ${age}, Type: ${typeof age}
Is Student: ${isStudent}, Type: ${typeof isStudent}
Null: ${nothing}, Type: ${typeof nothing}
Undefined: ${notDefined}, Type: ${typeof notDefined}
BigInt: ${bigNumber}, Type: ${typeof bigNumber}
Symbol: ${sym.toString()}, Type: ${typeof sym}
Person: ${JSON.stringify(person)}, Type: ${typeof person}
Array: ${numbers}, Type: ${typeof numbers}`;

document.getElementById('output').textContent = output;</code></pre>
  <div class="output" id="output"></div>
  <a href="index.html" class="btn">Back to Index</a>
  <div class="explanation">
    <h2>Explanation</h2>
    <ul>
      <li><b>let name = "Alice";</b> — Declares a string variable called <b>name</b>.</li>
      <li><b>let age = 25;</b> — Declares a number variable called <b>age</b>.</li>
      <li><b>let isStudent = true;</b> — Declares a boolean variable called <b>isStudent</b>.</li>
      <li><b>let nothing = null;</b> — <b>nothing</b> is explicitly set to <b>null</b> (no value).</li>
      <li><b>let notDefined;</b> — <b>notDefined</b> is declared but not assigned, so it is <b>undefined</b>.</li>
      <li><b>let bigNumber = 12345678901234567890n;</b> — <b>bigNumber</b> is a <b>BigInt</b> (large integer, note the <b>n</b> at the end).</li>
      <li><b>let sym = Symbol('unique');</b> — <b>sym</b> is a <b>Symbol</b>, a unique and immutable primitive value.</li>
      <li><b>let person = { name: "Bob", age: 30 };</b> — <b>person</b> is an object with properties <b>name</b> and <b>age</b>.</li>
      <li><b>let numbers = [1, 2, 3];</b> — <b>numbers</b> is an array.</li>
      <li>The <b>output</b> variable uses template literals and <b>typeof</b> to show each variable's value and type.</li>
      <li>The result is displayed in the green output box above.</li>
    </ul>
  </div>
  <script>
    let name = "Alice";
    let age = 25;
    let isStudent = true;
    let nothing = null;
    let notDefined;
    let bigNumber = 12345678901234567890n;
    let sym = Symbol('unique');
    let person = { name: "Bob", age: 30 };
    let numbers = [1, 2, 3];
    let output = `Name: ${name}, Type: ${typeof name}
Age: ${age}, Type: ${typeof age}
Is Student: ${isStudent}, Type: ${typeof isStudent}
Null: ${nothing}, Type: ${typeof nothing}
Undefined: ${notDefined}, Type: ${typeof notDefined}
BigInt: ${bigNumber}, Type: ${typeof bigNumber}
Symbol: ${sym.toString()}, Type: ${typeof sym}
Person: ${JSON.stringify(person)}, Type: ${typeof person}
Array: ${numbers}, Type: ${typeof numbers}`;
    document.getElementById('output').textContent = output;
  </script>
</body>
</html>