Dynamic fields form development for website

Form with Dynamic Fields Development

Dynamic fields are groups that user can add and remove while filling form. Typical scenarios: passenger list, order items, document co-authors.

Implementation via React Hook Form useFieldArray

import { useForm, useFieldArray, Controller } from 'react-hook-form';
import { z } from 'zod';
import { zodResolver } from '@hookform/resolvers/zod';

const passengerSchema = z.object({
  firstName: z.string().min(2),
  lastName:  z.string().min(2),
  birthDate: z.string(),
  passport:  z.string().regex(/^\d{4}\s\d{6}$/),
});

const formSchema = z.object({
  passengers: z.array(passengerSchema).min(1).max(9),
});

type FormValues = z.infer<typeof formSchema>;

export function PassengersForm() {
  const { control, register, handleSubmit, formState: { errors } } = useForm<FormValues>({
    resolver: zodResolver(formSchema),
    defaultValues: { passengers: [{}] },
  });

  const { fields, append, remove, move } = useFieldArray({
    control,
    name: 'passengers',
  });

  return (
    <form onSubmit={handleSubmit(console.log)}>
      <div className="space-y-4">
        {fields.map((field, index) => (
          <div key={field.id} className="border rounded-xl p-4 relative">
            <div className="flex items-center justify-between mb-3">
              <h3 className="font-medium">Passenger {index + 1}</h3>
              {fields.length > 1 && (
                <button
                  type="button"
                  onClick={() => remove(index)}
                  className="text-red-500 text-sm hover:text-red-700"
                >
                  Remove
                </button>
              )}
            </div>

            <div className="grid grid-cols-2 gap-3">
              <div>
                <label className="block text-sm mb-1">First Name</label>
                <input
                  {...register(`passengers.${index}.firstName`)}
                  className="input-field"
                />
                {errors.passengers?.[index]?.firstName && (
                  <p className="text-red-500 text-xs mt-1">
                    {errors.passengers[index].firstName?.message}
                  </p>
                )}
              </div>

              <div>
                <label className="block text-sm mb-1">Last Name</label>
                <input {...register(`passengers.${index}.lastName`)} className="input-field" />
              </div>

              <div>
                <label className="block text-sm mb-1">Passport</label>
                <input
                  {...register(`passengers.${index}.passport`)}
                  placeholder="1234 567890"
                  className="input-field"
                />
              </div>
            </div>
          </div>
        ))}
      </div>

      {fields.length < 9 && (
        <button
          type="button"
          onClick={() => append({})}
          className="btn-secondary mt-4 w-full"
        >
          + Add Passenger
        </button>
      )}

      <button type="submit" className="btn-primary mt-4 w-full">
        Continue
      </button>
    </form>
  );
}

Drag-and-Drop Sorting

For forms where element order matters (order items, task priorities):

import { DndContext, closestCenter } from '@dnd-kit/core';
import { SortableContext, verticalListSortingStrategy, useSortable } from '@dnd-kit/sortable';

function SortableFieldItem({ field, index, onRemove }: SortableItemProps) {
  const { attributes, listeners, setNodeRef, transform, transition } = useSortable({ id: field.id });

  return (
    <div ref={setNodeRef} style={{ transform: CSS.Transform.toString(transform), transition }}>
      <div {...attributes} {...listeners} className="cursor-grab p-1">⠿</div>
      {/* field items */}
    </div>
  );
}

// In main component:
function handleDragEnd(event) {
  const { active, over } = event;
  if (active.id !== over.id) {
    const from = fields.findIndex(f => f.id === active.id);
    const to   = fields.findIndex(f => f.id === over.id);
    move(from, to);
  }
}

Timeframe

Form with dynamic fields, add/remove and validation: 2–4 working days.