To create a QR code using HTML and JavaScript, you can use a JavaScript library like `qrcode.js`. Here’s a simple example of how to integrate it into an HTML page:
1. **Include the Library**: You need to include the `qrcode.js` library. You can either download it or use a CDN.
2. **Write the HTML and JavaScript Code**: Use the following code to create a QR code:
```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>QR Code Generator</title>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery.qrcode/1.0/jquery.qrcode.min.js"></script>
</head>
<body>
<h1>QR Code Generator</h1>
<input type="text" id="text-input" placeholder="Enter text here" />
<button onclick="generateQRCode()">Generate QR Code</button>
<div id="qrcode"></div>
<script>
function generateQRCode() {
const text = document.getElementById('text-input').value;
document.getElementById('qrcode').innerHTML = ''; // Clear previous QR code
if (text) {
$('#qrcode').qrcode({ text: text });
}
}
</script>
</body>
</html>
```
### Explanation:
- **Libraries**: The code includes jQuery and a QR code generation plugin for jQuery.
- **Input Field**: A text input where users can enter the data to be encoded.
- **Button**: A button that triggers the QR code generation.
- **QR Code Display**: A `div` where the QR code will be displayed.
- **JavaScript Function**: `generateQRCode` reads the input value and generates the QR code, clearing any previous codes first.
**Note**: Ensure you have internet access to load the libraries from the CDN, or you can host the libraries locally if preferred.