Real-time Field Validation

function onChange(control, oldValue, newValue, isLoading, isTemplate) {
  // Exit if form is loading
  if (isLoading) {
    return;
  }

  // Configuration: Define validation rules for different scenarios
  var fieldName = 'u_email';  // Change to your field name
  var value = newValue;

  // Clear any previous validation messages
  g_form.hideFieldMsg(fieldName, true);

  // Skip validation if field is empty
  if (!value || value === '') {
    return;
  }

  // Example 1: Email validation
  var emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
  if (!emailRegex.test(value)) {
    g_form.showFieldMsg(fieldName, 'Please enter a valid email address', 'error');
    return;
  }

  // Example 2: Phone number validation (US format)
  // Uncomment and modify for phone validation
  /*
  var phoneRegex = /^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$/;
  if (!phoneRegex.test(value)) {
    g_form.showFieldMsg('phone', 'Please enter a valid phone number (xxx-xxx-xxxx)', 'error');
    return;
  }
  */

  // Example 3: Minimum/Maximum length validation
  /*
  if (value.length < 5) {
    g_form.showFieldMsg(fieldName, 'Must be at least 5 characters long', 'error');
    return;
  }
  if (value.length > 100) {
    g_form.showFieldMsg(fieldName, 'Cannot exceed 100 characters', 'error');
    return;
  }
  */

  // Example 4: Numeric range validation
  /*
  var numValue = parseFloat(value);
  if (isNaN(numValue)) {
    g_form.showFieldMsg(fieldName, 'Please enter a valid number', 'error');
    return;
  }
  if (numValue < 0 || numValue > 100) {
    g_form.showFieldMsg(fieldName, 'Value must be between 0 and 100', 'error');
    return;
  }
  */

  // Example 5: URL validation
  /*
  var urlRegex = /^(https?:\/\/)?(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)$/;
  if (!urlRegex.test(value)) {
    g_form.showFieldMsg(fieldName, 'Please enter a valid URL', 'error');
    return;
  }
  */

  // Show success message (optional)
  g_form.showFieldMsg(fieldName, 'Valid email format', 'info');
}