base64_code_decode/index.html at main · veghadam/base64_code_decode · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Base64 Encoder/Decoder</title>
  <style>
    body {
      font-family: Arial, sans-serif;
      margin: 20px;
      max-width: 800px;
    }
    textarea {
      width: 100%;
      padding: 10px;
      margin-bottom: 20px;
      font-size: 1em;
      box-sizing: border-box;
    }
  </style>
</head>
<body>
  <h1>Base64 Encoder/Decoder</h1>
  <p>Paste text in the top textarea. If it is Base64 encoded, it will decode it; if not, it will encode it.</p>

  <!-- Input Textarea -->
  <textarea id="input" rows="10" placeholder="Paste text here..."></textarea>

  <!-- Output Textarea -->
  <textarea id="output" rows="10" placeholder="Result..." readonly></textarea>

  <script>
    /**
     * Checks if the given string is valid Base64.
     * It does this by removing whitespace, checking the length,
     * and trying to decode and re-encode the string.
     */
    function isValidBase64(str) {
      const sanitized = str.replace(/\s+/g, '');
      if (sanitized.length % 4 !== 0) {
        return false;
      }
      try {
        const decoded = atob(sanitized);
        return btoa(decoded) === sanitized;
      } catch (e) {
        return false;
      }
    }

    // Listen for input changes in the top textarea.
    document.getElementById('input').addEventListener('input', function() {
      const inputText = this.value.trim();
      const outputArea = document.getElementById('output');

      // Clear output if input is empty.
      if (inputText === '') {
        outputArea.value = '';
        return;
      }

      // If valid Base64, decode it.
      if (isValidBase64(inputText)) {
        try {
          outputArea.value = atob(inputText);
        } catch (e) {
          outputArea.value = 'Error decoding Base64: ' + e;
        }
      } else {
        // Otherwise, encode the text.
        try {
          outputArea.value = btoa(inputText);
        } catch (e) {
          outputArea.value = 'Error encoding to Base64: ' + e;
        }
      }
    });
  </script>
</body>
</html>