Working with Checkboxes, Radio Buttons, and Dropdowns

What common form pattern does this code implement?

function setupDependentSelects(parent, child, mapping) {
  parent.addEventListener('change', () => {
    const selectedValue = parent.value;
    child.innerHTML = '';
    mapping[selectedValue]?.forEach(option => {
      child.add(new Option(option.text, option.value));
    });
    child.disabled = !mapping[selectedValue];
  });
}

Basic validation
Cascading dropdowns
This implements cascading (or dependent) dropdowns, a common pattern where one select's options depend on another's selection. Features: 1) Updates child select based on parent's selection, 2) Clears and populates child options efficiently, 3) Handles the disabled state appropriately, 4) Uses Option constructor for clean option creation, 5) Supports optional chaining for safety. This pattern is crucial for forms where options in one field depend on the selection in another, like country/city or category/subcategory selections.
Option filtering
Data formatting

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