format credit card number javascript

<div class="container">
    <h1>Credit Card Formatter</h1>
    <p class="subtitle">Enter a card number to see it formatted automatically</p>

    <div class="input-group">
      <label for="cardInput">Card Number</label>
      <input 
        type="text" 
        id="cardInput" 
        placeholder="Enter card number"
        maxlength="19"
        autocomplete="off"
      >
    </div>

    <div class="card-display">
      <div class="card-type" id="cardType">CARD NUMBER</div>
      <div class="card-number" id="cardDisplay">
        <span class="card-placeholder">•••• •••• •••• ••••</span>
      </div>
    </div>

    <div class="info">
      <strong>Format:</strong> Automatically formats as you type<br>
      <strong>Example:</strong> 4532015112830366 → 4532 0151 1283 0366
    </div>
  </div>

  * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
      background: linear-gradient(135deg, #bdc3c7 0%, #2c3e50 100%);
      min-height: 100vh;
      display: flex;
      justify-content: center;
      align-items: center;
      padding: 20px;
    }

    .container {
      background: white;
      border-radius: 16px;
      box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
      padding: 40px;
      max-width: 500px;
      width: 100%;
    }

    h1 {
      font-size: 24px;
      color: #333;
      margin-bottom: 8px;
      font-weight: 600;
    }

    .subtitle {
      color: #666;
      font-size: 14px;
      margin-bottom: 32px;
    }

    .input-group {
      margin-bottom: 24px;
    }

    label {
      display: block;
      font-size: 14px;
      font-weight: 500;
      color: #333;
      margin-bottom: 8px;
    }

    input {
      width: 100%;
      padding: 14px 16px;
      font-size: 16px;
      border: 2px solid #e0e0e0;
      border-radius: 8px;
      transition: all 0.3s ease;
      font-family: 'Courier New', monospace;
      letter-spacing: 1px;
    }

    input:focus {
      outline: none;
      border-color: #a8a9ad;
      box-shadow: 0 0 0 3px rgba(189, 195, 199, 0.2);
    }

    .card-display {
      background: linear-gradient(135deg, #d7d2cc 0%, #304352 100%);
      border-radius: 12px;
      padding: 24px;
      margin-top: 24px;
      color: white;
      min-height: 140px;
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
    }

    .card-type {
      font-size: 12px;
      text-transform: uppercase;
      letter-spacing: 1px;
      opacity: 0.9;
    }

    .card-number {
      font-size: 22px;
      font-family: 'Courier New', monospace;
      letter-spacing: 2px;
      margin-top: 20px;
      font-weight: 500;
    }

    .card-placeholder {
      opacity: 0.5;
    }

    .info {
      margin-top: 16px;
      padding: 12px;
      background: #f5f5f5;
      border-radius: 8px;
      font-size: 13px;
      color: #666;
    }

    .info strong {
      color: #333;
    }

  const cardInput = document.getElementById('cardInput');
    const cardDisplay = document.getElementById('cardDisplay');
    const cardType = document.getElementById('cardType');

    function formatCardNumber(value) {
      const digitsOnly = value.replace(/\D/g, '');
      const formatted = digitsOnly.match(/.{1,4}/g);
      return formatted ? formatted.join(' ') : '';
    }

    function detectCardType(number) {
      const patterns = {
        visa: /^4/,
        mastercard: /^5[1-5]/,
        amex: /^3[47]/,
        discover: /^6(?:011|5)/
      };

      for (let [type, pattern] of Object.entries(patterns)) {
        if (pattern.test(number)) return type.toUpperCase();
      }

      return 'CARD NUMBER';
    }

    cardInput.addEventListener('input', (e) => {
      let value = e.target.value;
      const formatted = formatCardNumber(value);
      e.target.value = formatted;

      if (formatted) {
        cardDisplay.innerHTML = formatted;
        cardDisplay.classList.remove('card-placeholder');
        const digitsOnly = formatted.replace(/\s/g, '');
        cardType.textContent = detectCardType(digitsOnly);
      } else {
        cardDisplay.innerHTML = '<span class="card-placeholder">•••• •••• •••• ••••</span>';
        cardType.textContent = 'CARD NUMBER';
      }
    });

    cardInput.addEventListener('paste', (e) => {
      setTimeout(() => {
        e.target.dispatchEvent(new Event('input'));
      }, 0);
    });