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

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Async JavaScript - 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>Async JavaScript</h1>
  <pre><code>function fetchData(callback) {
    setTimeout(() => {
        callback("Data received");
    }, 1000);
}

function fetchDataPromise() {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve("Promise resolved");
        }, 1000);
    });
}

async function getData() {
    let data = await fetchDataPromise();
    return data;
}

let output = "Starting async operations...\n";

fetchData((data) => {
    output += `Callback: ${data}\n`;
    document.getElementById('output').textContent = output;
});

fetchDataPromise().then(data => {
    output += `Promise: ${data}\n`;
    document.getElementById('output').textContent = output;
});

getData().then(data => {
    output += `Async/Await: ${data}`;
    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>fetchData(callback)</b> — Simulates an async operation using a callback.</li>
      <li><b>fetchDataPromise()</b> — Returns a Promise that resolves after 1 second.</li>
      <li><b>getData()</b> — Uses async/await to wait for the Promise to resolve.</li>
      <li>Shows how to handle async code with callbacks, Promises, and async/await.</li>
      <li>The <b>output</b> variable collects the results and is displayed in the green output box above.</li>
    </ul>
  </div>
  <script>
    function fetchData(callback) {
      setTimeout(() => {
        callback("Data received");
      }, 1000);
    }
    function fetchDataPromise() {
      return new Promise((resolve) => {
        setTimeout(() => {
          resolve("Promise resolved");
        }, 1000);
      });
    }
    async function getData() {
      let data = await fetchDataPromise();
      return data;
    }
    let output = "Starting async operations...\n";
    fetchData((data) => {
      output += `Callback: ${data}\n`;
      document.getElementById('output').textContent = output;
    });
    fetchDataPromise().then(data => {
      output += `Promise: ${data}\n`;
      document.getElementById('output').textContent = output;
    });
    getData().then(data => {
      output += `Async/Await: ${data}`;
      document.getElementById('output').textContent = output;
    });
  </script>
</body>
</html>